samples: boards: nordic: clock_control: add README.rst

Add documentation of the nordic clock control sample in the form of
a README.rst

Signed-off-by: Bjarki Arge Andreasen <[email protected]>

Author: bjarki-andreasen

samples/boards/nordic/clock_control/README.rst

@@ -0,0 +1,60 @@
+.. zephyr:code-sample:: nrf_clock_control
+   :name: nRF clock control
+
+    Request minimum clock requirements at runtime.
+
+Demonstrates how to request minimum clock requirements of nordic clocks, including getting the
+startup time to ensure clock requirements are met in time.
+
+Requirements
+************
+
+Requires a nRF54H20 based board.
+
+Building, Flashing and Running
+******************************
+
+The sample is built to test a specific clock requirement for a specific clock. The clock is
+specified in a devicetree overlay, and the clock requirement is defined using these sample
+specific Kconfigs:
+
+* :kconfig:option:`CONFIG_SAMPLE_CLOCK_FREQUENCY_HZ`
+* :kconfig:option:`CONFIG_SAMPLE_CLOCK_ACCURACY_PPM`
+* :kconfig:option:`CONFIG_SAMPLE_CLOCK_PRECISION`
+
+With the following controlling how long the request is held:
+
+* :kconfig:option:`CONFIG_SAMPLE_PRE_REQUEST_TIMEOUT`
+* :kconfig:option:`CONFIG_SAMPLE_KEEP_REQUEST_TIMEOUT`
+
+Example configs and overlays are added for every clock, which can be found in :file:`sample.yaml`,
+and applied using the ``-T`` west argument. The following example builds the sample to test the
+FLL16M:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/boards/nordic/clock_control
+   :board: nrf54h20dk/nrf54h20/cpuapp
+   :goals: build
+   :west-args: -T sample.boards.nrf.clock_control.fll16m
+   :compact:
+
+Example output:
+
+.. code-block:: none
+
+   clock name: fll16m
+   minimum frequency request: 0Hz
+   minimum accuracy request: 30PPM
+   minimum precision request: 0
+
+   resolved frequency request: 16000000Hz
+   resolved accuracy request: 30PPM
+   resolved precision request: 0
+
+   startup time for requested spec: 850us
+
+   requesting minimum clock specs
+   request applied to clock in 1ms
+
+   releasing requested clock specs
+   clock spec request released