dt-bindings: serial: imx: Document wakeup-source property

The i.MX UART can be used as a wake-up source, document the 'wakeup-source'
property as allowed property.

Signed-off-by: Marek Vasut <[email protected]>
Acked-by: Conor Dooley <[email protected]>
Reviewed-by: Fabio Estevam <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Marek Vasut

Documentation/devicetree/bindings/serial/fsl-imx-uart.yaml

@@ -70,6 +70,8 @@ properties:
   interrupts:
     maxItems: 1
 
+  wakeup-source: true
+
   fsl,dte-mode:
     $ref: /schemas/types.yaml#/definitions/flag
     description: |