Harness: Power harness documentation

Add documentation for power harness.

Signed-off-by: Arkadiusz Cholewinski <arkadiuszx.cholewinski@intel.com>

Author: gbarkadiusz

doc/develop/test/twister.rst

@@ -561,6 +561,7 @@ harness: <string>
     - robot
     - ctest
     - shell
+    - power
 
     See :ref:`twister_harnesses` for more information.
 
@@ -972,6 +973,44 @@ robot_testsuite: <robot file path> (default empty)
 robot_option: <robot option> (default empty)
     One or more options to be send to robotframework.
 
+Power
+=====
+The ``power`` harness is used to measure and validate the current consumption.
+It integrates with 'pytest' to perform automated data collection and analysis using a hardware power monitor.
+
+The harness executes the following steps:
+
+1. Initializes a power monitoring device (e.g., ``stm_powershield``) via the ``PowerMonitor`` abstract interface.
+#. Starts current measurement for a defined ``measurement_duration``.
+#. Collects raw current waveform data.
+#. Uses a peak detection algorithm to segment data into defined execution phases based on power transitions.
+#. Computes RMS current values for each phase using a utility function.
+#. Compares the computed values with user-defined expected RMS values.
+
+.. code-block:: yaml
+
+    harness: power
+    harness_config:
+      fixture: pm_probe
+      power_measurements:
+        element_to_trim: 100
+        min_peak_distance: 40
+        min_peak_height: 0.008
+        peak_padding: 40
+        measurement_duration: 6
+        num_of_transitions: 4
+        expected_rms_values: [56.0, 4.0, 1.2, 0.26, 140]
+        tolerance_percentage: 20
+
+- **elements_to_trim** – Number of samples to discard at the start of measurement to eliminate noise.
+- **min_peak_distance** – Minimum distance between detected current peaks (helps detect distinct transitions).
+- **min_peak_height** – Minimum current threshold to qualify as a peak (in amps).
+- **peak_padding** – Number of samples to extend around each detected peak.
+- **measurement_duration** – Total time (in seconds) to record current data.
+- **num_of_transitions** – Expected number of power state transitions in the DUT during test execution.
+- **expected_rms_values** – Target RMS values for each identified execution phase (in milliamps).
+- **tolerance_percentage** – Allowed deviation percentage from the expected RMS values.
+
 Bsim
 ====