diff --git a/doc/releases/migration-guide-4.2.rst b/doc/releases/migration-guide-4.2.rst
index 8ef5726d065..c50064190e7 100644
--- a/doc/releases/migration-guide-4.2.rst
+++ b/doc/releases/migration-guide-4.2.rst
@@ -272,6 +272,14 @@ Bluetooth Audio
 * ``CONFIG_BT_CSIP_SET_MEMBER_NOTIFIABLE`` has been renamed to
   :kconfig:option:`CONFIG_BT_CSIP_SET_MEMBER_SIRK_NOTIFIABLE``. (:github:`86763``)
 
+Bluetooth HCI
+=============
+
+* The buffer types passing through the HCI driver interface are now indicated as H:4 encoded prefix
+  bytes as part of the buffer payload itself. The bt_buf_set_type() and bt_buf_get_type() functions
+  have been deprecated, but are still usable, with the exception that they can only be
+  called once per buffer.
+
 Bluetooth Host
 ==============