* ST Keyscan controller Device Tree bindings

The ST keyscan controller Device Tree binding is based on the
matrix-keymap.

Required properties:
- compatible: "st,sti-keyscan"

- reg: Register base address and size of st-keyscan controller.

- interrupts: Interrupt number for the st-keyscan controller.

- clocks: Must contain one entry, for the module clock.
  See ../clocks/clock-bindings.txt for details.

- pinctrl: Should specify pin control groups used for this controller.
  See ../pinctrl/pinctrl-bindings.txt for details.

- linux,keymap: The keymap for keys as described in the binding document
  devicetree/bindings/input/matrix-keymap.txt.

- keypad,num-rows: Number of row lines connected to the keypad controller.

- keypad,num-columns: Number of column lines connected to the keypad
  controller.

Optional property:
- st,debounce_us: Debouncing interval time in microseconds

Example:

keyscan: keyscan@fe4b0000 {
	compatible = "st,sti-keyscan";
	reg = <0xfe4b0000 0x2000>;
	interrupts = <GIC_SPI 212 IRQ_TYPE_NONE>;
	clocks	= <&CLK_SYSIN>;
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_keyscan>;

	keypad,num-rows = <4>;
	keypad,num-columns = <4>;
	st,debounce_us = <5000>;

	linux,keymap = < MATRIX_KEY(0x00, 0x00, KEY_F13)
			 MATRIX_KEY(0x00, 0x01, KEY_F9)
			 MATRIX_KEY(0x00, 0x02, KEY_F5)
			 MATRIX_KEY(0x00, 0x03, KEY_F1)
			 MATRIX_KEY(0x01, 0x00, KEY_F14)
			 MATRIX_KEY(0x01, 0x01, KEY_F10)
			 MATRIX_KEY(0x01, 0x02, KEY_F6)
			 MATRIX_KEY(0x01, 0x03, KEY_F2)
			 MATRIX_KEY(0x02, 0x00, KEY_F15)
			 MATRIX_KEY(0x02, 0x01, KEY_F11)
			 MATRIX_KEY(0x02, 0x02, KEY_F7)
			 MATRIX_KEY(0x02, 0x03, KEY_F3)
			 MATRIX_KEY(0x03, 0x00, KEY_F16)
			 MATRIX_KEY(0x03, 0x01, KEY_F12)
			 MATRIX_KEY(0x03, 0x02, KEY_F8)
			 MATRIX_KEY(0x03, 0x03, KEY_F4) >;
	};