doc: release-notes-4.1: complete list of notable changes

Add details about:
- Driver API improvements with iterable sections and device API checking
- Enhanced board catalog with hardware feature search and generation of
  table of supported hardware features

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

Author: kartben

doc/releases/release-notes-4.1.rst

@@ -985,3 +985,14 @@ Other notable changes
   by excluding the test scenario name prefix which is the same as the parent test suite id.
 
 * Added support for HTTP PUT/PATCH/DELETE methods for HTTP server dynamic resources.
+
+* Driver API structures are now available through iterable sections and a new
+  :c:macro:`DEVICE_API_IS` macro has been introduced to allow to check if a device supports a
+  given API. Many shell commands now use this to provide "smarter" auto-completion and only list
+  compatible devices when they expect a device argument.
+
+* Zephyr's :ref:`interactive board catalog <boards>` has been extended to allow searching for boards
+  based on supported hardware features. A new :rst:dir:`zephyr:board-supported-hw` Sphinx directive
+  can now be used in boards' documentation pages to automatically include a list of the hardware
+  features supported by a board, and many boards have already adopted this new feature in their
+  documentation.