doc: samples: added documentation for the new radio_test command

added documentation for the new radio_test command as well as a
changelog entry

Signed-off-by: Thomas Johansen <thomas.johansen@nordicsemi.no>

Author: thomas-m-johansen

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

@@ -718,7 +718,10 @@ nRF5340 samples
 Peripheral samples
 ------------------
 
-|no_changes_yet_note|
+* :ref:`radio_test` sample:
+
+  * Added the new ``start_tx_sweep_duty_cycle`` shell command.
+    It allows for running a TX sweep with silent periods between each frequency.
 
 PMIC samples
 ------------

samples/peripheral/radio_test/README.rst

@@ -129,6 +129,12 @@ User interface
    * - time_on_channel
      - <time>
      - Time on each channel in ms (between 1 and 99).
+   * - start_tx_sweep_duty_cycle
+     -
+     - Start TX sweep with duty cycle
+   * - sweep_duty_cycle_timings
+     - <tx_time> <sleep_time>
+     - Time reserved for transmission and sleep respectively on each channel in us.
    * - toggle_dcdc_state
      - <state>
      - Toggle DC/DC converter state.