dt-bindings: Document Broadcom Cygnus SoC and clocks

Reviewed-by: Arun Parameswaran <[e-mail]>
Tested-by: Jonathan Richardson <[e-mail]>
Reviewed-by: JD (Jiandong) Zheng <[e-mail]>
Reviewed-by: Ray Jui <[e-mail]>
Signed-off-by: Scott Branden <[e-mail]>

Documentation/devicetree/bindings/arm/bcm/cygnus.txt

···
+Broadcom Cygnus device tree bindings
+------------------------------------
+
+
+Boards with Cygnus SoCs shall have the following properties:
+
+Required root node property:
+
+BCM11300
+compatible = "brcm,bcm11300", "brcm,cygnus";
+
+BCM11320
+compatible = "brcm,bcm11320", "brcm,cygnus";
+
+BCM11350
+compatible = "brcm,bcm11350", "brcm,cygnus";
+
+BCM11360
+compatible = "brcm,bcm11360", "brcm,cygnus";
+
+BCM58300
+compatible = "brcm,bcm58300", "brcm,cygnus";
+
+BCM58302
+compatible = "brcm,bcm58302", "brcm,cygnus";
+
+BCM58303
+compatible = "brcm,bcm58303", "brcm,cygnus";
+
+BCM58305
+compatible = "brcm,bcm58305", "brcm,cygnus";

Documentation/devicetree/bindings/clock/bcm-cygnus-clock.txt

···
+Broadcom Cygnus Clocks
+
+This binding uses the common clock binding:
+Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+Currently various "fixed" clocks are declared for peripheral drivers that use
+the common clock framework to reference their core clocks. Proper support of
+these clocks will be added later
+
+Device tree example:
+
+	clocks {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges;
+
+		osc: oscillator {
+			compatible = "fixed-clock";
+			#clock-cells = <1>;
+			clock-frequency = <25000000>;
+		};
+
+		apb_clk: apb_clk {
+			compatible = "fixed-clock";
+			#clock-cells = <0>;
+			clock-frequency = <1000000000>;
+		};
+
+		periph_clk: periph_clk {
+			compatible = "fixed-clock";
+			#clock-cells = <0>;
+			clock-frequency = <500000000>;
+		};
+	};