diff --git a/include/image.mk b/include/image.mk
index a4ac1b49cf..9a4dff2167 100644
--- a/include/image.mk
+++ b/include/image.mk
@@ -21,6 +21,11 @@ include $(INCLUDE_DIR)/rootfs.mk
 override MAKE:=$(_SINGLE)$(SUBMAKE)
 override NO_TRACE_MAKE:=$(_SINGLE)$(NO_TRACE_MAKE)
 
+##@
+# @brief Convert size with unit postfix to unitless expression in bytes.
+#
+# @param 1: Size with unit. Possible unit postfix are `g`, `m`, `k`.
+##
 exp_units = $(subst k, * 1024,$(subst m, * 1024k,$(subst g, * 1024m,$(1))))
 
 target_params = $(subst +,$(space),$*)
@@ -111,6 +116,12 @@ endef
 
 PROFILE_SANITIZED := $(call tolower,$(subst DEVICE_,,$(subst $(space),-,$(PROFILE))))
 
+##@
+# @brief Call function for each group of arguments.
+#
+# @param 1: List of lists of arguments. Lists are separated by `|`.
+# @param 2: Function to call for list of arguments.
+##
 define split_args
 $(foreach data, \
 	$(subst |,$(space),\
@@ -118,12 +129,24 @@ $(foreach data, \
 	$(call $(2),$(strip $(subst ^,$(space),$(data)))))
 endef
 
+##@
+# @brief Call build function with arguments.
+#
+# @param 1: Function to call. Function name is prepended with `Build/`.
+# @param 2...: Function arguments.
+##
 define build_cmd
 $(if $(Build/$(word 1,$(1))),,$(error Missing Build/$(word 1,$(1))))
 $(call Build/$(word 1,$(1)),$(wordlist 2,$(words $(1)),$(1)))
 
 endef
 
+##@
+# @brief Call build functions from the list.
+#
+# @param 1: List of build functions with arguments, separated by `|`.
+#           First word in each group is a build command without `Build/` prefix.
+##
 define concat_cmd
 $(call split_args,$(1),build_cmd)
 endef
@@ -163,6 +186,12 @@ DTC_WARN_FLAGS := \
 DTC_FLAGS += $(DTC_WARN_FLAGS)
 DTCO_FLAGS += $(DTC_WARN_FLAGS)
 
+##@
+# @brief Pad file to specified size.
+#
+# @param 1: File.
+# @param 2: Padding.
+##
 define Image/pad-to
 	dd if=$(1) of=$(1).new bs=$(2) conv=sync
 	mv $(1).new $(1)
@@ -403,26 +432,53 @@ define Device/InitProfile
   DEVICE_DESCRIPTION = Build firmware images for $$(DEVICE_TITLE)
 endef
 
+##@
+# @brief Image configuration variables.
+#
+# @param 1: Device name.
+##
 define Device/Init
+  ##@ Device name.
   DEVICE_NAME := $(1)
+  ##@ Commands to build kernel.
+  # Commands with arguments are separated by `|`.
+  ##
   KERNEL:=
+  ##@ Commands to build initramfs.
+  # Commands with arguments are separated by `|`.
+  ##
   KERNEL_INITRAMFS = $$(KERNEL)
+  ##@ Kernel command line.
   CMDLINE:=
 
+  ##@ Images to build.
   IMAGES :=
+  ##@ Artifacts to build.
   ARTIFACTS :=
+  ##@ Device image prefix.
   DEVICE_IMG_PREFIX := $(IMG_PREFIX)-$(1)
+  ##@ Device image name.
   DEVICE_IMG_NAME = $$(DEVICE_IMG_PREFIX)-$$(1)-$$(2)
+  ##@ Factory image name.
   FACTORY_IMG_NAME :=
+  ##@ Maximum image size. Optional.
   IMAGE_SIZE :=
+  ##@ Maximum image size. Optional.
   NAND_SIZE :=
+  ##@ Kernel image prefix.
   KERNEL_PREFIX = $$(DEVICE_IMG_PREFIX)
+  ##@ Kernel image suffix.
   KERNEL_SUFFIX := -kernel.bin
+  ##@ Initramfs image suffix.
   KERNEL_INITRAMFS_SUFFIX = $$(KERNEL_SUFFIX)
+  ##@ Kernel image name.
   KERNEL_IMAGE = $$(KERNEL_PREFIX)$$(KERNEL_SUFFIX)
+  ##@ Initramfs image prefix.
   KERNEL_INITRAMFS_PREFIX = $$(DEVICE_IMG_PREFIX)-initramfs
   KERNEL_INITRAMFS_IMAGE = $$(KERNEL_INITRAMFS_PREFIX)$$(KERNEL_INITRAMFS_SUFFIX)
+  ##@ Initramfs image name.
   KERNEL_INITRAMFS_NAME = $$(KERNEL_NAME)-initramfs
+  ##@ Kernel install flag.
   KERNEL_INSTALL :=
   KERNEL_NAME := vmlinux
   KERNEL_DEPENDS :=
diff --git a/include/target.mk b/include/target.mk
index 3dc0acff5c..02ea68b15c 100644
--- a/include/target.mk
+++ b/include/target.mk
@@ -7,10 +7,17 @@ ifneq ($(__target_inc),1)
 __target_inc=1
 
 
-# default device type
+##@
+# @brief Default device type ( basic | nas | router ).
+##
 DEVICE_TYPE?=router
 
-# Default packages - the really basic set
+##@
+# @brief Default packages.
+#
+# The really basic set. Additional packages are added based on @DEVICE_TYPE and
+# @CONFIG_* values.
+##
 DEFAULT_PACKAGES:=\
 	base-files \
 	ca-bundle \
@@ -27,15 +34,21 @@ DEFAULT_PACKAGES:=\
 	urandom-seed \
 	urngd
 
-# For the basic set
+##@
+# @brief Default packages for @DEVICE_TYPE basic.
+##
 DEFAULT_PACKAGES.basic:=
-# For nas targets
+##@
+# @brief Default packages for @DEVICE_TYPE nas.
+##
 DEFAULT_PACKAGES.nas:=\
 	block-mount \
 	fdisk \
 	lsblk \
 	mdadm
-# For router targets
+##@
+# @brief Default packages for @DEVICE_TYPE router.
+##
 DEFAULT_PACKAGES.router:=\
 	dnsmasq \
 	firewall4 \
@@ -85,7 +98,18 @@ endif
 # Add device specific packages (here below to allow device type set from subtarget)
 DEFAULT_PACKAGES += $(DEFAULT_PACKAGES.$(DEVICE_TYPE))
 
+##@
+# @brief Filter out packages, prepended with `-`.
+#
+# @param 1: Package list.
+##
 filter_packages = $(filter-out -% $(patsubst -%,%,$(filter -%,$(1))),$(1))
+
+##@
+# @brief Append extra package dependencies.
+#
+# @param 1: Package list.
+##
 extra_packages = $(if $(filter wpad wpad-% nas,$(1)),iwinfo)
 
 define ProfileDefault
diff --git a/rules.mk b/rules.mk
index 973fd1cbb9..54df407fca 100644
--- a/rules.mk
+++ b/rules.mk
@@ -20,6 +20,11 @@ endif
 export TMP_DIR:=$(TOPDIR)/tmp
 export TMPDIR:=$(TMP_DIR)
 
+##@
+# @brief Strip quotes `"` and pounds `#` from string.
+#
+# @param 1: String.
+##
 qstrip=$(strip $(subst ",,$(1)))
 #"))
 
@@ -27,8 +32,23 @@ empty:=
 space:= $(empty) $(empty)
 comma:=,
 pound:=\#
+##@
+# @brief Merge strings by removing spaces.
+#
+# @param 1: String.
+##
 merge=$(subst $(space),,$(1))
+##@
+# @brief Get hash sum of variable list.
+#
+# @param 1: List of variable names.
+##
 confvar=$(shell echo '$(foreach v,$(1),$(v)=$(subst ','\'',$($(v))))' | $(MKHASH) md5)
+##@
+# @brief Strip last extension from file name.
+#
+# @param 1: File name.
+##
 strip_last=$(patsubst %.$(lastword $(subst .,$(space),$(1))),%,$(1))
 
 paren_left = (
@@ -51,9 +71,18 @@ __tr_head = $(subst $(paren_left)subst,$(paren_left)subst$(space),$(__tr_head_st
 __tr_tail = $(subst $(space),,$(foreach cv,$(1),$(paren_right)))
 __tr_template = $(__tr_head)$$(1)$(__tr_tail)
 
+##@
+# @brief Convert string characters to upper.
+##
 $(eval toupper = $(call __tr_template,$(chars_lower),$(chars_upper)))
+##@
+# @brief Convert string characters to lower.
+##
 $(eval tolower = $(call __tr_template,$(chars_upper),$(chars_lower)))
 
+##@
+# @brief Abbreviate version. Truncate to 8 characters.
+##
 version_abbrev = $(if $(if $(CHECK),,$(DUMP)),$(1),$(shell printf '%.8s' $(1)))
 
 _SINGLE=export MAKEFLAGS=$(space);
@@ -102,6 +131,13 @@ endif
 
 DEFAULT_SUBDIR_TARGETS:=clean download prepare compile update refresh prereq dist distcheck configure check check-depends
 
+##@
+# @brief Create default targets.
+#
+# Targets are created from @DEFAULT_SUBDIR_TARGETS and input argument lists.
+#
+# @param 1: Additional targets list.
+##
 define DefaultTargets
 $(foreach t,$(DEFAULT_SUBDIR_TARGETS) $(1),
   .$(t):
@@ -371,16 +407,28 @@ export BISON_PKGDATADIR:=$(STAGING_DIR_HOST)/share/bison
 export HOST_GNULIB_SRCDIR:=$(STAGING_DIR_HOST)/share/gnulib
 export M4:=$(STAGING_DIR_HOST)/bin/m4
 
+##@
+# @brief Slugify variable name and prepend suffix.
+##
 define shvar
 V_$(subst .,_,$(subst -,_,$(subst /,_,$(1))))
 endef
 
+##@
+# @brief Create and export variable, set to function result.
+#
+# @param 1: Function name. Used as variable name, prepended with `V_`.
+##
 define shexport
 export $(call shvar,$(1))=$$(call $(1))
 endef
 
+##@
+# @brief Support 64 bit tine in C code.
+#
 # Test support for 64-bit time with C code from largefile.m4 provided by GNU Gnulib
-# the value is 'y' when successful and '' otherwise
+# the value is `y` when successful and `` otherwise
+##
 define YEAR_2038
 $(shell \
   mkdir -p $(TMP_DIR); \
@@ -392,9 +440,12 @@ $(shell \
 )
 endef
 
-# Execute commands under flock
-# $(1) => The shell expression.
-# $(2) => The lock name. If not given, the global lock will be used.
+##@
+# @brief Execute commands under flock
+#
+# @param 1: The shell expression.
+# @param 2: The lock name. If not given, the global lock will be used.
+##
 ifneq ($(wildcard $(STAGING_DIR_HOST)/bin/flock),)
   define locked
 	SHELL= \
@@ -406,10 +457,14 @@ else
   locked=$(1)
 endif
 
-# Recursively copy paths into another directory, purge dangling
+
+##@
+# @brief Recursively copy paths into another directory, purge dangling
 # symlinks before.
-# $(1) => File glob expression
-# $(2) => Destination directory
+#
+# @param 1: File glob expression.
+# @param 1: Destination directory.
+##
 define file_copy
 	for src_dir in $(sort $(foreach d,$(wildcard $(1)),$(dir $(d)))); do \
 		( cd $$src_dir; find -type f -or -type d ) | \
@@ -424,19 +479,30 @@ define file_copy
 	$(CP) $(1) $(2)
 endef
 
-# Calculate sha256sum of any plain file within a given directory
-# $(1) => Input directory
-# $(2) => If set, recurse into subdirectories
+##@
+# @brief Calculate sha256sum of any plain file within a given directory.
+#
+# @param 1: Input directory.
+# @param 2: If set, recurse into subdirectories.
+##
 define sha256sums
 	(cd $(1); find . $(if $(2),,-maxdepth 1) -type f -not -name 'sha256sums' -printf "%P\n" | sort | \
 		xargs -r $(MKHASH) -n sha256 | sed -ne 's!^\(.*\) \(.*\)$$!\1 *\2!p' > sha256sums)
 endef
 
-# file extension
+##@
+# @brief Retrieve file extension.
+#
+# @param 1: File name.
+##
 ext=$(word $(words $(subst ., ,$(1))),$(subst ., ,$(1)))
 
-# Count Git commits of a package
-# $(1) => if non-empty: count commits since last ": [uU]pdate to " or ": [bB]ump to " in commit message
+##@
+# @brief Count Git commits of a package.
+#
+# @param 1: if non-empty: count commits since last ": [uU]pdate to "
+#           or ": [bB]ump to " in commit message.
+##
 define commitcount
 $(shell \
   if git log -1 >/dev/null 2>/dev/null; then \
@@ -458,6 +524,11 @@ $(shell \
 )
 endef
 
+##@
+# @brief Get ABI version string, stripping `-`, `_` and `.`.
+#
+# @param 1: Version string.
+##
 abi_version_str = $(subst -,,$(subst _,,$(subst .,,$(1))))
 
 COMMITCOUNT = $(if $(DUMP),0,$(call commitcount))