i2c: sh_mobile: Add per-Generation fallback bindings

Add per-Generation fallback bindings for R-Car SoCs.

This is in keeping with the compatibility string scheme is being adopted
for drivers for Renesas SoCs.

Also, improve readability by listing the rmobile fallback compatibility
string after the more-specific compatibility strings they provide a
fallback for.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-sh_mobile.txt

 Device tree configuration for Renesas IIC (sh_mobile) driver
 
 Required properties:
-- compatible      : "renesas,iic-<soctype>". "renesas,rmobile-iic" as fallback
-		     Examples with soctypes are:
+- compatible      :
 			- "renesas,iic-r8a73a4" (R-Mobile APE6)
 			- "renesas,iic-r8a7740" (R-Mobile A1)
 			- "renesas,iic-r8a7790" (R-Car H2)
@@ -12,6 +11,17 @@ Required properties:
 			- "renesas,iic-r8a7794" (R-Car E2)
 			- "renesas,iic-r8a7795" (R-Car H3)
 			- "renesas,iic-sh73a0" (SH-Mobile AG5)
+			- "renesas,rcar-gen2-iic" (generic R-Car Gen2 compatible device)
+			- "renesas,rcar-gen3-iic" (generic R-Car Gen3 compatible device)
+			- "renesas,rmobile-iic" (generic device)
+
+			When compatible with a generic R-Car version, nodes
+			must list the SoC-specific version corresponding to
+			the platform first followed by the generic R-Car
+			version.
+
+			renesas,rmobile-iic must always follow.
+
 - reg             : address start and address range size of device
 - interrupts      : interrupt of device
 - clocks          : clock for device
@@ -31,7 +41,8 @@ Pinctrl properties might be needed, too. See there.
 Example:
 
 	iic0: i2c@e6500000 {
-		compatible = "renesas,iic-r8a7790", "renesas,rmobile-iic";
+		compatible = "renesas,iic-r8a7790", "renesas,rcar-gen2-iic",
+			     "renesas,rmobile-iic";
 		reg = <0 0xe6500000 0 0x425>;
 		interrupts = <0 174 IRQ_TYPE_LEVEL_HIGH>;
 		clocks = <&mstp3_clks R8A7790_CLK_IIC0>;

drivers/i2c/busses/i2c-sh_mobile.c

@@ -827,7 +827,6 @@ static const struct sh_mobile_dt_config r8a7740_dt_config = {
 };
 
 static const struct of_device_id sh_mobile_i2c_dt_ids[] = {
-	{ .compatible = "renesas,rmobile-iic", .data = &default_dt_config },
 	{ .compatible = "renesas,iic-r8a73a4", .data = &fast_clock_dt_config },
 	{ .compatible = "renesas,iic-r8a7740", .data = &r8a7740_dt_config },
 	{ .compatible = "renesas,iic-r8a7790", .data = &fast_clock_dt_config },
@@ -835,8 +834,11 @@ static const struct of_device_id sh_mobile_i2c_dt_ids[] = {
 	{ .compatible = "renesas,iic-r8a7792", .data = &fast_clock_dt_config },
 	{ .compatible = "renesas,iic-r8a7793", .data = &fast_clock_dt_config },
 	{ .compatible = "renesas,iic-r8a7794", .data = &fast_clock_dt_config },
+	{ .compatible = "renesas,rcar-gen2-iic", .data = &fast_clock_dt_config },
 	{ .compatible = "renesas,iic-r8a7795", .data = &fast_clock_dt_config },
+	{ .compatible = "renesas,rcar-gen3-iic", .data = &fast_clock_dt_config },
 	{ .compatible = "renesas,iic-sh73a0", .data = &fast_clock_dt_config },
+	{ .compatible = "renesas,rmobile-iic", .data = &default_dt_config },
 	{},
 };
 MODULE_DEVICE_TABLE(of, sh_mobile_i2c_dt_ids);