Docs/risc-v/esp32[-c3|-c6|-h2]: Add autopm docs

Add autopm docs for risc-v based Espressif devices

Signed-off-by: Eren Terzioglu <eren.terzioglu@espressif.com>

Documentation/platforms/risc-v/esp32c3/boards/esp32c3-devkit/index.rst

@@ -74,6 +74,18 @@ show in units of mV)::
     3: channel: 2 value: 0
     4: channel: 3 value: 0
 
+autopm
+------
+
+This configuration makes the device automatically enter the low power consumption mode
+when in the idle state, powering off the cpu and other peripherals.
+
+In minimum power save mode, the station wakes up every DTIM to receive a beacon. The broadcast
+data will not be lost because it is transmitted after DTIM. However, it can not save much more
+power if DTIM is short as the DTIM is determined by the access point.
+
+During ping operation power consumption should drop from 90-100mA to 40-50mA.
+
 ble
 ---
 

Documentation/platforms/risc-v/esp32c6/boards/esp32c6-devkitc/index.rst

@@ -109,6 +109,18 @@ show in units of mV)::
     3: channel: 2 value: 103
     4: channel: 3 value: 104
 
+autopm
+------
+
+This configuration makes the device automatically enter the low power consumption mode
+when in the idle state, powering off the cpu and other peripherals.
+
+In minimum power save mode, the station wakes up every DTIM to receive a beacon. The broadcast
+data will not be lost because it is transmitted after DTIM. However, it can not save much more
+power if DTIM is short as the DTIM is determined by the access point.
+
+During ping operation power consumption should drop from 90-100mA to 30-40mA.
+
 bmp180
 ------
 

Documentation/platforms/risc-v/esp32h2/boards/esp32h2-devkit/index.rst

@@ -108,6 +108,12 @@ show in units of mV)::
     3: channel: 2 value: 1
     4: channel: 3 value: 0
 
+autopm
+------
+
+This configuration makes the device automatically enter the low power consumption mode
+when in the idle state, powering off the cpu and other peripherals.
+
 bmp180
 ------