[nrf fromtree] doc: releases: introduce release notes and migration guide docs for 4.1

This introduces the release notes and migration guide for 4.1.0 earlier
than we typically do, so that people have a placeholder to start adding
content as they line up pull requests for 4.1.
The two documents are currently orphan and not visible from the main
documentation as this would confuse users of 4.0.

Signed-off-by: Benjamin Cabé <[email protected]>
(cherry picked from commit d342f9e)

Author: kartben

doc/releases/migration-guide-4.1.rst

@@ -0,0 +1,112 @@
+:orphan:
+
+.. _migration_4.1:
+
+Migration guide to Zephyr v4.1.0 (Working Draft)
+################################################
+
+This document describes the changes required when migrating your application from Zephyr v4.0.0 to
+Zephyr v4.1.0.
+
+Any other changes (not directly related to migrating applications) can be found in
+the :ref:`release notes<zephyr_4.1>`.
+
+.. contents::
+    :local:
+    :depth: 2
+
+Build System
+************
+
+Kernel
+******
+
+Boards
+******
+
+Modules
+*******
+
+Mbed TLS
+========
+
+Trusted Firmware-M
+==================
+
+LVGL
+====
+
+Device Drivers and Devicetree
+*****************************
+
+Controller Area Network (CAN)
+=============================
+
+Display
+=======
+
+Enhanced Serial Peripheral Interface (eSPI)
+===========================================
+
+GNSS
+====
+
+Input
+=====
+
+Interrupt Controller
+====================
+
+LED Strip
+=========
+
+Sensors
+=======
+
+Serial
+======
+
+Regulator
+=========
+
+Bluetooth
+*********
+
+Bluetooth HCI
+=============
+
+Bluetooth Mesh
+==============
+
+Bluetooth Audio
+===============
+
+Bluetooth Classic
+=================
+
+Bluetooth Host
+==============
+
+Bluetooth Crypto
+================
+
+Networking
+**********
+
+Other Subsystems
+****************
+
+Flash map
+=========
+
+hawkBit
+=======
+
+MCUmgr
+======
+
+Modem
+=====
+
+Architectures
+*************