PM / Domains: Add DT bindings for the R-Car System Controller

The Renesas R-Car System Controller provides power management for the
CPU cores and various coprocessors, following the generic PM domain
bindings in Documentation/devicetree/bindings/power/power_domain.txt.

This supports R-Car Gen1 (H1), Gen2, and Gen3.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

Documentation/devicetree/bindings/power/renesas,rcar-sysc.txt

+DT bindings for the Renesas R-Car System Controller
+
+== System Controller Node ==
+
+The R-Car System Controller provides power management for the CPU cores and
+various coprocessors.
+
+Required properties:
+  - compatible: Must contain exactly one of the following:
+      - "renesas,r8a7779-sysc" (R-Car H1)
+      - "renesas,r8a7790-sysc" (R-Car H2)
+      - "renesas,r8a7791-sysc" (R-Car M2-W)
+      - "renesas,r8a7792-sysc" (R-Car V2H)
+      - "renesas,r8a7793-sysc" (R-Car M2-N)
+      - "renesas,r8a7794-sysc" (R-Car E2)
+      - "renesas,r8a7795-sysc" (R-Car H3)
+  - reg: Address start and address range for the device.
+  - #power-domain-cells: Must be 1.
+
+
+Example:
+
+	sysc: system-controller@e6180000 {
+		compatible = "renesas,r8a7791-sysc";
+		reg = <0 0xe6180000 0 0x0200>;
+		#power-domain-cells = <1>;
+	};
+
+
+== PM Domain Consumers ==
+
+Devices residing in a power area must refer to that power area, as documented
+by the generic PM domain bindings in
+Documentation/devicetree/bindings/power/power_domain.txt.
+
+Required properties:
+  - power-domains: A phandle and symbolic PM domain specifier, as defined in
+		   <dt-bindings/power/r8a77*-sysc.h>.
+
+
+Example:
+
+	L2_CA15: cache-controller@0 {
+		compatible = "cache";
+		power-domains = <&sysc R8A7791_PD_CA15_SCU>;
+		cache-unified;
+		cache-level = <2>;
+	};