dt-bindings: serial: renesas,em-uart: Document r9a09g011 bindings

The Renesas RZ/V2M (r9a09g011) SoC uses a uart that is compatible with the
EMMA Mobile SoC.
Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20220330154024.112270-3-phil.edworthy@renesas.comAcked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/renesas,em-uart.yaml

@@ -14,7 +14,14 @@ allOf:
 
 properties:
   compatible:
-    const: renesas,em-uart
+    oneOf:
+      - items:
+          - enum:
+              - renesas,r9a09g011-uart    # RZ/V2M
+          - const: renesas,em-uart        # generic EMMA Mobile compatible UART
+
+      - items:
+          - const: renesas,em-uart        # generic EMMA Mobile compatible UART
 
   reg:
     maxItems: 1