Closes #22507: document that PyType_IsSubtype does not call __subclasscheck__.
diff --git a/Doc/c-api/type.rst b/Doc/c-api/type.rst
index 22f7dd0..957cccf 100644
--- a/Doc/c-api/type.rst
+++ b/Doc/c-api/type.rst
@@ -71,6 +71,11 @@
.. versionadded:: 2.2
+ This function only checks for actual subtypes, which means that
+ :meth:`~type.__subclasscheck__` is not called on *b*. Call
+ :c:func:`PyObject_IsSubclass` to do the same check that :func:`issubclass`
+ would do.
+
.. c:function:: PyObject* PyType_GenericAlloc(PyTypeObject *type, Py_ssize_t nitems)