* Freescale Quad Serial Peripheral Interface(QuadSPI)

The QuadSPI controller acts as the SPI master. It is described with a node
for the controller and a set of child nodes for each SPI NOR flash.

Part I - The DT node for the controller:
------------------------------

Required properties:
  - compatible : Should be "fsl,vf610-qspi", "fsl,imx6sx-qspi",
		 "fsl,imx7d-qspi", "fsl,imx6ul-qspi",
		 "fsl,ls1021a-qspi"
		 or
		 "fsl,ls2080a-qspi" followed by "fsl,ls1021a-qspi",
		 "fsl,ls1043a-qspi" followed by "fsl,ls1021a-qspi"
  - reg : the first contains the register location and length,
          the second contains the memory mapping address and length
  - reg-names: Should contain the reg names "QuadSPI" and "QuadSPI-memory"
  - interrupts : Should contain the interrupt for the device
  - clocks : The clocks needed by the QuadSPI controller
  - clock-names : the name of the clocks

Optional properties:
  - fsl,qspi-has-second-chip: The controller has two buses, bus A and bus B.
                              Each bus can be connected with two NOR flashes.
			      Most of the time, each bus only has one NOR flash
			      connected, this is the default case.
			      But if there are two NOR flashes connected to the
			      bus, you should enable this property.
			      (Please check the board's schematic.)
  - big-endian : That means the IP register is big endian

Part II - The DT nodes for each SPI NOR flash
------------------------------
Required properties:
- spi-max-frequency : Maximum frequency of the SPI bus the chip can operate at

Optional properties:
  Please refer to the Documentation/devicetree/bindings/mtd/spi-nor-flash.txt
  If you set the "spi-nor,ddr-quad-read-dummy", it means you enable the DDR
  quad read feature for the driver.

Example:

qspi0: quadspi@40044000 {
	compatible = "fsl,vf610-qspi";
	reg = <0x40044000 0x1000>, <0x20000000 0x10000000>;
	reg-names = "QuadSPI", "QuadSPI-memory";
	interrupts = <0 24 IRQ_TYPE_LEVEL_HIGH>;
	clocks = <&clks VF610_CLK_QSPI0_EN>,
		<&clks VF610_CLK_QSPI0>;
	clock-names = "qspi_en", "qspi";

	flash0: s25fl128s@0 {
		....
	};
};