dt-bindings: mtd: describe BCM963XX ImageTag format and usage

Broadcom BCM963XX ImageTag Partition Container

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

Some Broadcom BCM63XX SoC based devices contain additional, non discoverable

partitions or non standard bootloader partition sizes. For these a mixed layout

needs to be used with an explicit firmware partition.

The BCM963XX ImageTag is a simple firmware header describing the offsets and

sizes of the rootfs and kernel parts contained in the firmware.

Required properties:

- compatible : must be "brcm,bcm963xx-imagetag"

Example:

flash@1e000000 {

	compatible = "cfi-flash";

	reg = <0x1e000000 0x2000000>;

	bank-width = <2>;

	partitions {

		compatible = "fixed-partitions";

		#address-cells = <1>;

		#size-cells = <1>;

		cfe@0 {

			reg = <0x0 0x10000>;

			read-only;

		};

		firmware@10000 {

			reg = <0x10000 0x7d0000>;

			compatible = "brcm,bcm963xx-imagetag";

		};

		caldata@7e0000 {

			reg = <0x7e0000 0x10000>;

			read-only;

		};

		nvram@7f0000 {

			reg = <0x7f0000 0x10000>;

		};

	};

};