dt-bindings: Document Broadcom Cygnus SoC and clocks

Broadcom Cygnus device tree bindings

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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";

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>;

		};

	};