dt-bindings: openrisc: Add OpenRISC platform SoC

OpenRISC Generic SoC

====================

Boards and FPGA SoC's which support the OpenRISC standard platform.  The

platform essentially follows the conventions of the OpenRISC architecture

specification, however some aspects, such as the boot protocol have been defined

by the Linux port.

Required properties

-------------------

 - compatible: Must include "opencores,or1ksim"

CPU nodes:

----------

A "cpus" node is required.  Required properties:

 - #address-cells: Must be 1.

 - #size-cells: Must be 0.

A CPU sub-node is also required for at least CPU 0.  Since the topology may

be probed via CPS, it is not necessary to specify secondary CPUs.  Required

properties:

 - compatible: Must be "opencores,or1200-rtlsvn481".

 - reg: CPU number.

 - clock-frequency: The CPU clock frequency in Hz.

Example:

	cpus {

		#address-cells = <1>;

		#size-cells = <0>;

		cpu@0 {

			compatible = "opencores,or1200-rtlsvn481";

			reg = <0>;

			clock-frequency = <20000000>;

		};

	};

Boot protocol

-------------

The bootloader may pass the following arguments to the kernel:

 - r3:  address of a flattened device-tree blob or 0x0.

L:	openrisc@lists.librecores.org

W:	http://openrisc.io

S:	Maintained

F:	Documentation/devicetree/bindings/openrisc/

F:	Documentation/openrisc/

F:	arch/openrisc/

F:	drivers/irqchip/irq-or1k-*