diff --git a/DOCS/interface-changes/user-data-subpath.txt b/DOCS/interface-changes/user-data-subpath.txt
new file mode 100644
index 0000000000..160d9fb0fe
--- /dev/null
+++ b/DOCS/interface-changes/user-data-subpath.txt
@@ -0,0 +1 @@
+reserve `user-data/osc` and `user-data/mpv` sub-paths for internal use
diff --git a/DOCS/man/input.rst b/DOCS/man/input.rst
index 0b279f1c1c..8ddd196ad9 100644
--- a/DOCS/man/input.rst
+++ b/DOCS/man/input.rst
@@ -3549,6 +3549,12 @@ Property list
     The player itself does not use any data in it (although some builtin scripts may).
     The property is not preserved across player restarts.
 
+    The following sub-paths are reserved for internal uses or have special semantics:
+    ``user-data/osc``, ``user-data/mpv``. Unless noted otherwise, the semantics of
+    any properties under these sub-paths can change at any time and may not be relied
+    upon, and writing to these properties may prevent builtin scripts from working
+    properly.
+
     Sub-paths can be accessed directly; e.g. ``user-data/my-script/state/a`` can be
     read, written, or observed.