docs: migration-guide-4.3: Add TF-M sign note

Add note about BL2 (MCUboot) signing updates when board is build as
TF-M NS.

Signed-off-by: BUDKE Gerson Fernando <[email protected]>

Author: nandojve

doc/releases/migration-guide-4.3.rst

@@ -255,5 +255,26 @@ Silabs
 * The separate ``em3`` power state was removed from Series 2 SoCs. The system automatically
   transitions to EM2 or EM3 depending on hardware peripheral requests for the oscillators.
 
+Trusted Firmware-M
+==================
+
+* The signing process for BL2 (MCUboot) was updated. The boards that run using
+  TF-M NS and require BL2 must have their flash layout with the flash controller
+  information. This will ensures that when signing the hex/bin files all the
+  details will be present in the S and NS images. With this new constraint, the
+  image now has the details to allow the FWU state machine be correct and allow
+  FOTA.
+  (:github:`94470`)
+
+    * The ``--align`` parameter was fixed and still provides 1 as a fallback for specific vendors.
+    * The ``--max-sectors`` value is now calculated based on the number of images, taking into
+      consideration the largest image size.
+    * The ``--confirm`` option now confirms both S and NS HEX images, ensuring that any image
+      that runs is valid for production and development.
+    * S and NS BIN images are now available. These are the correct images to be used in FOTA. Note
+      that S and NS images are unconfirmed by default, and the application is responsible for
+      confirming them with ``psa_fwu_accept()``. Otherwise, the images will roll back on the next
+      reboot.
+
 Architectures
 *************