usb: host: xhci-plat: add R-Car Gen2 and Gen3 fallback compatibility strings

Add fallback compatibility strings for R-Car Gen2 and Gen3.

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: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/usb-xhci.txt

 USB xHCI controllers
 
 Required properties:
-  - compatible: should be one of "generic-xhci",
-    "marvell,armada-375-xhci", "marvell,armada-380-xhci",
-    "renesas,xhci-r8a7790", "renesas,xhci-r8a7791", "renesas,xhci-r8a7793",
-    "renesas,xhci-r8a7795" (deprecated: "xhci-platform").
+  - compatible: should be one or more of
+
+    - "generic-xhci" for generic XHCI device
+    - "marvell,armada-375-xhci" for Armada 375 SoCs
+    - "marvell,armada-380-xhci" for Armada 38x SoCs
+    - "renesas,xhci-r8a7790" for r8a7790 SoC
+    - "renesas,xhci-r8a7791" for r8a7791 SoC
+    - "renesas,xhci-r8a7793" for r8a7793 SoC
+    - "renesas,xhci-r8a7795" for r8a7795 SoC
+    - "renesas,rcar-gen2-xhci" for a generic R-Car Gen2 compatible device
+    - "renesas,rcar-gen3-xhci" for a generic R-Car Gen3 compatible device
+    - "xhci-platform" (deprecated)
+
+    When compatible with the generic version, nodes must list the
+    SoC-specific version corresponding to the platform first
+    followed by the generic version.
+
   - reg: should contain address and length of the standard XHCI
     register set for the device.
   - interrupts: one XHCI interrupt should be described here.

drivers/usb/host/xhci-plat.c

@@ -110,6 +110,11 @@ static const struct of_device_id usb_xhci_of_match[] = {
 		.compatible = "renesas,xhci-r8a7795",
 		.data = &xhci_plat_renesas_rcar_gen3,
 	}, {
+		.compatible = "renesas,rcar-gen2-xhci",
+		.data = &xhci_plat_renesas_rcar_gen2,
+	}, {
+		.compatible = "renesas,rcar-gen3-xhci",
+		.data = &xhci_plat_renesas_rcar_gen3,
 	},
 };
 MODULE_DEVICE_TABLE(of, usb_xhci_of_match);