Update Changelog

Author: rwgk

docs/changelog.rst

@@ -15,7 +15,18 @@ IN DEVELOPMENT
 
 Changes will be summarized here periodically.
 
-Version 2.12.0 (March 27, 2025)
+Version 2.12.1 (September 13, 2024)
+-----------------------------------
+
+New Features:
+
+* Backport of PR #5296: The pybind11 v2.12 series now interoperates with other
+  pybind11 versions that include PR #5296. (See the description of PR #5296 for
+  limitations.)
+  `#5368 <https://github.com/pybind/pybind11/pull/5368>`_
+
+
+Version 2.12.0 (March 27, 2024)
 -------------------------------
 
 New Features: