ravb: add fallback compatibility strings

Add fallback compatibility strings for R-Car Gen 2 & 3 SoC Families.
This is in keeping with the fallback scheme being adopted wherever appropriate
for drivers for Renesas SoCs.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/renesas,ravb.txt

@@ -7,6 +7,13 @@ Required properties:
 - compatible: "renesas,etheravb-r8a7790" if the device is a part of R8A7790 SoC.
 	      "renesas,etheravb-r8a7794" if the device is a part of R8A7794 SoC.
 	      "renesas,etheravb-r8a7795" if the device is a part of R8A7795 SoC.
+	      "renesas,etheravb-rcar-gen2" for generic R-Car Gen 2 compatible interface.
+	      "renesas,etheravb-rcar-gen3" for generic R-Car Gen 3 compatible interface.
+
+	      When compatible with the generic version, nodes must list the
+	      SoC-specific version corresponding to the platform first
+	      followed by the generic version.
+
 - reg: offset and length of (1) the register block and (2) the stream buffer.
 - interrupts: A list of interrupt-specifiers, one for each entry in
 	      interrupt-names.
@@ -37,7 +44,7 @@ Optional properties:
 Example:
 
 	ethernet@e6800000 {
-		compatible = "renesas,etheravb-r8a7795";
+		compatible = "renesas,etheravb-r8a7795", "renesas,etheravb-rcar-gen3";
 		reg = <0 0xe6800000 0 0x800>, <0 0xe6a00000 0 0x10000>;
 		interrupt-parent = <&gic>;
 		interrupts = <GIC_SPI 39 IRQ_TYPE_LEVEL_HIGH>,

drivers/net/ethernet/renesas/ravb_main.c

@@ -1659,7 +1659,9 @@ static int ravb_mdio_release(struct ravb_private *priv)
 static const struct of_device_id ravb_match_table[] = {
 	{ .compatible = "renesas,etheravb-r8a7790", .data = (void *)RCAR_GEN2 },
 	{ .compatible = "renesas,etheravb-r8a7794", .data = (void *)RCAR_GEN2 },
+	{ .compatible = "renesas,etheravb-rcar-gen2", .data = (void *)RCAR_GEN2 },
 	{ .compatible = "renesas,etheravb-r8a7795", .data = (void *)RCAR_GEN3 },
+	{ .compatible = "renesas,etheravb-rcar-gen3", .data = (void *)RCAR_GEN3 },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, ravb_match_table);