doc: Add a release note entry for switching to picolibc

Added a release note entry to infrom that Matter and Thread
samples switched to picolibc.

Signed-off-by: Arkadiusz Balys <[email protected]>

Author: ArekBalysNordic

doc/nrf/releases_and_maturity/known_issues.rst

@@ -607,16 +607,18 @@ The issues in this section are related to the :ref:`ug_matter` protocol.
 
 .. rst-class:: v3-1-1
 
-KRKNWK-20774: Fatal error on nRF54LM20 SoC after enabling the :kconfig:option:`CONFIG_PICOLIBC` Kconfig option or dynamic heap memory allocation
+KRKNWK-20774: Fatal error on the nRF54LM20 SoC after enabling the :kconfig:option:`CONFIG_PICOLIBC` Kconfig option or dynamic heap memory allocation
   The nRF54LM20 SoC crashes after enabling the :kconfig:option:`CONFIG_PICOLIBC` Kconfig option or dynamic heap memory allocation while running a Matter sample.
   The root cause is that the nRF54LM20 DK devicetree overlay in the Matter samples configures the SRAM memory incorrectly.
   As a result, a restricted region of the SRAM is used, which leads to a crash.
 
+  **Affected platforms:** nRF54LM20
+
   **Workaround:** Remove the following configuration from the :file:`boards/nrf54lm20dk_nrf54lm20a_cpuapp.overlay`, :file:`boards/nrf54lm20dk_nrf54lm20a_cpuapp_internal.overlay`, :file:`sysbuild/mcuboot/boards/nrf54lm20dk_nrf54lm20a_cpuapp.conf`, and :file:`sysbuild/mcuboot/boards/nrf54lm20dk_nrf54lm20a_cpuapp_internal.conf` files of the Matter sample:
 
     .. code-block:: console
 
-      /* restore full RRAM and SRAM space - by default some parts are dedicated to FLRP */
+      /* Restore full RRAM and SRAM space. By default, some parts are dedicated to FLRP. */
       &cpuapp_rram {
         reg = <0x0 DT_SIZE_K(2036)>;
       };

doc/nrf/releases_and_maturity/releases/release-notes-changelog.rst

@@ -179,7 +179,7 @@ Gazell
 Matter
 ------
 
-|no_changes_yet_note|
+* Updated to using the :kconfig:option:`CONFIG_PICOLIBC` Kconfig option as the C library instead of :kconfig:option:`CONFIG_NEWLIB_LIBC`, in compliance with Zephyr requirements.
 
 Matter fork
 +++++++++++
@@ -194,7 +194,10 @@ nRF IEEE 802.15.4 radio driver
 Thread
 ------
 
-* Updated the :ref:`thread_sed_ssed` documentation to clarify the impact of the SSED configuration on the device's power consumption and provide a guide for :ref:`thread_ssed_fine_tuning` of SSED devices.
+* Updated:
+
+  * The :ref:`thread_sed_ssed` documentation to clarify the impact of the SSED configuration on the device's power consumption and provide a guide for :ref:`thread_ssed_fine_tuning` of SSED devices.
+  * The platform configuration to use the :kconfig:option:`CONFIG_PICOLIBC` Kconfig opiton as the C library instead of :kconfig:option:`CONFIG_NEWLIB_LIBC`, in compliance with Zephyr requirements.
 
 Wi-Fi®
 ------