opensbi: add package for RISC-V

OpenSBI is a form of a first-stage bootloader, which initializes
certain parts of an SoC and then passes on control to the second
stage bootloader i.e. an u-boot image.

We're introducing the package with release v1.2, which provides
SBI v0.3 and the SBI SRST extensions which helps to gracefully
reboot/shutdown various HiFive-U SoCs.

Tested on SiFive Unleashed and Unmatched boards.

Signed-off-by: Zoltan HERPAI <wigyori@uid0.hu>

package/boot/opensbi/Makefile

@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Copyright (C) 2022 OpenWrt.org
+#
+
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=opensbi
+PKG_RELEASE:=1.2
+
+PKG_SOURCE_PROTO:=git
+PKG_SOURCE_URL=https://github.com/riscv/opensbi
+PKG_SOURCE_DATE:=2022-12-24
+PKG_SOURCE_VERSION:=6b5188ca14e59ce7bf71afe4e7d3d557c3d31bf8
+PKG_MIRROR_HASH:=edcdd99da6c62975171981c0aa2b73a27091067da11ccd49816b5ad27d000858
+
+PKG_BUILD_DIR=$(BUILD_DIR)/$(PKG_NAME)-$(BUILD_VARIANT)/$(PKG_NAME)-$(PKG_VERSION)
+
+PKG_TARGETS:=bin
+PKG_FLAGS:=nonshared
+PKG_LICENSE:=BSD-2-Clause
+PKG_LICENSE_FILES:=COPYING.BSD
+PKG_BUILD_PARALLEL:=1
+
+PKG_MAINTAINER:=Zoltan HERPAI <wigyori@uid0.hu>
+
+include $(INCLUDE_DIR)/package.mk
+
+define Package/opensbi
+    SECTION:=boot
+    CATEGORY:=Boot Loaders
+    DEPENDS:=@TARGET_sifiveu
+    URL:=https://github.com/riscv/opensbi/blob/master/README.md
+    VARIANT:=$(subst _,/,$(subst opensbi_,,$(1)))
+    TITLE:=OpenSBI generic
+    OPENSBI_IMAGE:=
+    PLAT:=
+endef
+
+define Package/opensbi_generic
+  $(Package/opensbi)
+  TITLE:=OpenSBI generic
+  OPENSBI_IMAGE:=fw_dynamic.bin
+  PLAT:=generic
+endef
+
+export GCC_HONOUR_COPTS=s
+
+MAKE_VARS = \
+	CROSS_COMPILE="$(TARGET_CROSS)"
+
+define Build/Compile
+	$(eval $(Package/opensbi_$(BUILD_VARIANT))) \
+		+$(MAKE_VARS) $(MAKE) -C $(PKG_BUILD_DIR) \
+		PLATFORM=$(PLAT)
+endef
+
+define Build/InstallDev
+	$(INSTALL_DIR) $(STAGING_DIR_IMAGE)
+	$(CP) $(PKG_BUILD_DIR)/build/platform/$(PLAT)/firmware/fw_dynamic.bin $(STAGING_DIR_IMAGE)/fw_dynamic-${BUILD_VARIANT}.bin
+endef
+
+$(eval $(call BuildPackage,opensbi_generic))