dt-bindings: serial: stm32: add power-domains property

STM32 serial may be in a power domain.
Allow a single 'power-domains' entry for STM32 serial devices.

Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240118091135.3314330-1-valentin.caron@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: VCASTM

Documentation/devicetree/bindings/serial/st,stm32-uart.yaml

@@ -58,6 +58,9 @@ properties:
 
   wakeup-source: true
 
+  power-domains:
+    maxItems: 1
+
   rx-threshold:
     description:
       If value is set to 1, RX FIFO threshold is disabled.