dt-bindings: Add bindings for Broadcom STB DRAM Sensors

DDR PHY Front End (DPFE) for Broadcom STB

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DPFE and the DPFE firmware provide an interface for the host CPU to

communicate with the DCPU, which resides inside the DDR PHY.

There are three memory regions for interacting with the DCPU. These are

specified in a single reg property.

Required properties:

  - compatible: must be "brcm,bcm7271-dpfe-cpu", "brcm,bcm7268-dpfe-cpu"

    or "brcm,dpfe-cpu"

  - reg: must reference three register ranges

      - start address and length of the DCPU register space

      - start address and length of the DCPU data memory space

      - start address and length of the DCPU instruction memory space

  - reg-names: must contain "dpfe-cpu", "dpfe-dmem", and "dpfe-imem";

        they must be in the same order as the register declarations

Example:

	dpfe_cpu0: dpfe-cpu@f1132000 {

		compatible = "brcm,bcm7271-dpfe-cpu", "brcm,dpfe-cpu";

		reg =  <0xf1132000 0x180

			0xf1134000 0x1000

			0xf1138000 0x4000>;

		reg-names = "dpfe-cpu", "dpfe-dmem", "dpfe-imem";

	};