ChromeOS Firmware

This node specifies information of ChromeOS verified-boot firmware.  The
firmware might update this node prior to booting the kernel.

Required properties:

  - write-protect-gpio : Describe the write-protect GPIO of the system.
  - recovery-gpio : Describe the recovery  GPIO of the system.
  - nonvolatile-context-storage : Storage device type that firmware used for
    vboot nonvolatile context.  It should be one of "disk", "mkbp", or "nvram".
    Kernel should look for the device that firmware actually used in the
    corresponding optional property below.

Optional properties:

  - chromeos-vbc-blk : If nonvolatile-context-storage is "disk", kernel should
    look for the block device used for storing vboot context in this property.
    It is a 4-tuple of block device phandle, LBA of the block storing vboot
    context, byte offset in the block, and size of vboot context in bytes.
  - chromeos-vbc-ec : If nonvolatile-context-storage is "mkbp", kernel should
    look for the phandle to the device tree node of EC in this property.

Example:

firmware {
	chromeos {
		write-protect-gpio = <&gpd1 6 0 0x10000 0>;
		nonvolatile-context-storage = "disk";
		chromeos-vbc-blk = <&mshc_0 0 0 16>;
		chromeos-vbc-ec = <&ec>;
	};
};