caf: power_manager: Document Kconfig changes

Change adds documentation for introduced Kconfig configuration changes.

Jira: NCSDK-32519

Signed-off-by: Marek Pieta <Marek.Pieta@nordicsemi.no>
Signed-off-by: Divya Pillai <divya.pillai@nordicsemi.no>

Author: MarekPieta

doc/nrf/libraries/caf/power_manager.rst

@@ -15,7 +15,26 @@ Configuration
 
 To enable the |power_manager|, set the :kconfig:option:`CONFIG_CAF_POWER_MANAGER` Kconfig option in the configuration.
 
-This module uses Zephyr's :ref:`zephyr:pm_api` subsystem.
+Implied features
+================
+
+The :kconfig:option:`CONFIG_CAF_POWER_MANAGER` option implies the following features that can be used to reduce power consumption:
+
+* System power off support (:kconfig:option:`CONFIG_POWEROFF`).
+  The option is not implied for an nRF54H Series SoC (:kconfig:option:`CONFIG_SOC_SERIES_NRF54HX`), because the :c:func:`sys_poweroff` API is not yet fully supported on the nRF54H Series SoC.
+* Device Power Management (:kconfig:option:`CONFIG_PM_DEVICE`).
+
+nRF54H Series SoC
+-----------------
+
+For the nRF54H Series SoC (:kconfig:option:`CONFIG_SOC_SERIES_NRF54HX`), the module also implies the following features:
+
+* Zephyr's :ref:`zephyr:pm-system` (:kconfig:option:`CONFIG_PM`).
+  The nRF54H Series SoC (:kconfig:option:`CONFIG_SOC_SERIES_NRF54HX`) integrates the system power management to reduce power consumption when inactive.
+* Zephyr's :ref:`zephyr:pm-device-runtime` (:kconfig:option:`CONFIG_PM_DEVICE_RUNTIME`).
+  The feature can be used to reduce power consumption of device drivers.
+  Enabling the device runtime power management also prevents using system-managed device power management (:kconfig:option:`CONFIG_PM_DEVICE_SYSTEM_MANAGED`) by default.
+  The system-managed device power management does not work properly with some drivers (for example, nrfx UARTE) and should be avoided.
 
 Timeout configuration options
 =============================

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

@@ -790,6 +790,17 @@ Common Application Framework
     Earlier, only **GPIO0** and **GPIO1** devices were supported.
     Now, the generic solution supports all GPIOs available in the DTS.
 
+* :ref:`caf_power_manager`:
+
+  * Updated:
+
+    * The :kconfig:option:`CONFIG_CAF_POWER_MANAGER` Kconfig option to imply the device power management (:kconfig:option:`CONFIG_DEVICE_PM`) instead of selecting it.
+      The device power management is not required by the module.
+    * The :kconfig:option:`CONFIG_CAF_POWER_MANAGER` Kconfig option to imply device runtime power management (:kconfig:option:`CONFIG_PM_DEVICE_RUNTIME`) for the nRF54H Series SoC (:kconfig:option:`CONFIG_SOC_SERIES_NRF54HX`).
+      The feature can be used to reduce the power consumption of device drivers.
+      Enabling the device runtime power management also prevents using system-managed device power management (:kconfig:option:`CONFIG_PM_DEVICE_SYSTEM_MANAGED`) by default.
+      The system-managed device power management does not work properly with some drivers (for example, nrfx UARTE) and should be avoided.
+
 Debug libraries
 ---------------