dt-bindings: Add a binding for Mediatek SCP

Mediatek SCP Bindings

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This binding provides support for ARM Cortex M4 Co-processor found on some

Mediatek SoCs.

Required properties:

- compatible		Should be "mediatek,mt8183-scp"

- reg			Should contain the address ranges for the two memory

			regions, SRAM and CFG.

- reg-names		Contains the corresponding names for the two memory

			regions. These should be named "sram" & "cfg".

- clocks		Clock for co-processor (See: ../clock/clock-bindings.txt)

- clock-names		Contains the corresponding name for the clock. This

			should be named "main".

Subnodes

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Subnodes of the SCP represent rpmsg devices. The names of the devices are not

important. The properties of these nodes are defined by the individual bindings

for the rpmsg devices - but must contain the following property:

- mtk,rpmsg-name	Contains the name for the rpmsg device. Used to match

			the subnode to rpmsg device announced by SCP.

Example:

	scp: scp@10500000 {

		compatible = "mediatek,mt8183-scp";

		reg = <0 0x10500000 0 0x80000>,

		      <0 0x105c0000 0 0x5000>;

		reg-names = "sram", "cfg";

		clocks = <&infracfg CLK_INFRA_SCPSYS>;

		clock-names = "main";

	};