mtd: spi-nor: Bindings for Cadence Quad SPI Flash Controller driver

* Cadence Quad SPI controller

Required properties:

- compatible : Should be "cdns,qspi-nor".

- reg : Contains two entries, each of which is a tuple consisting of a

	physical address and length. The first entry is the address and

	length of the controller register set. The second entry is the

	address and length of the QSPI Controller data area.

- interrupts : Unit interrupt specifier for the controller interrupt.

- clocks : phandle to the Quad SPI clock.

- cdns,fifo-depth : Size of the data FIFO in words.

- cdns,fifo-width : Bus width of the data FIFO in bytes.

- cdns,trigger-address : 32-bit indirect AHB trigger address.

Optional properties:

- cdns,is-decoded-cs : Flag to indicate whether decoder is used or not.

Optional subnodes:

Subnodes of the Cadence Quad SPI controller are spi slave nodes with additional

custom properties:

- cdns,read-delay : Delay for read capture logic, in clock cycles

- cdns,tshsl-ns : Delay in nanoseconds for the length that the master

                  mode chip select outputs are de-asserted between

		  transactions.

- cdns,tsd2d-ns : Delay in nanoseconds between one chip select being

                  de-activated and the activation of another.

- cdns,tchsh-ns : Delay in nanoseconds between last bit of current

                  transaction and deasserting the device chip select

		  (qspi_n_ss_out).

- cdns,tslch-ns : Delay in nanoseconds between setting qspi_n_ss_out low

                  and first bit transfer.

Example:

	qspi: spi@ff705000 {

		compatible = "cdns,qspi-nor";

		#address-cells = <1>;

		#size-cells = <0>;

		reg = <0xff705000 0x1000>,

		      <0xffa00000 0x1000>;

		interrupts = <0 151 4>;

		clocks = <&qspi_clk>;

		cdns,is-decoded-cs;

		cdns,fifo-depth = <128>;

		cdns,fifo-width = <4>;

		cdns,trigger-address = <0x00000000>;

		flash0: n25q00@0 {

			...

			cdns,read-delay = <4>;

			cdns,tshsl-ns = <50>;

			cdns,tsd2d-ns = <50>;

			cdns,tchsh-ns = <4>;

			cdns,tslch-ns = <4>;

		};

	};