serial: sh-sci: document R8A77970 bindings

R-Car V3M (R8A77970) SoC also has the R-Car gen3 compatible SCIF and HSCIF
ports, so document the SoC specific bindings.
Signed-off-by: NSergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: NRob Herring <robh@kernel.org>
Acked-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Acked-by: NSimon Horman <horms+renesas@verge.net.au>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/renesas,sci-serial.txt

@@ -41,6 +41,8 @@ Required properties:
     - "renesas,hscif-r8a7795" for R8A7795 (R-Car H3) HSCIF compatible UART.
     - "renesas,scif-r8a7796" for R8A7796 (R-Car M3-W) SCIF compatible UART.
     - "renesas,hscif-r8a7796" for R8A7796 (R-Car M3-W) HSCIF compatible UART.
+    - "renesas,scif-r8a77970" for R8A77970 (R-Car V3M) SCIF compatible UART.
+    - "renesas,hscif-r8a77970" for R8A77970 (R-Car V3M) HSCIF compatible UART.
     - "renesas,scif-r8a77995" for R8A77995 (R-Car D3) SCIF compatible UART.
     - "renesas,hscif-r8a77995" for R8A77995 (R-Car D3) HSCIF compatible UART.
     - "renesas,scifa-sh73a0" for SH73A0 (SH-Mobile AG5) SCIFA compatible UART.