Sitronix ST7789V RGB panel with SPI control bus

Required properties:
  - compatible: "sitronix,st7789v"
  - reg: Chip select of the panel on the SPI bus
  - reset-gpios: a GPIO phandle for the reset pin
  - power-supply: phandle of the regulator that provides the supply voltage

Optional properties:
  - backlight: phandle to the backlight used

The generic bindings for the SPI slaves documented in [1] also applies

The device node can contain one 'port' child node with one child
'endpoint' node, according to the bindings defined in [2]. This
node should describe panel's video bus.

[1]: Documentation/devicetree/bindings/spi/spi-bus.txt
[2]: Documentation/devicetree/bindings/graph.txt

Example:

panel@0 {
	compatible = "sitronix,st7789v";
	reg = <0>;
	reset-gpios = <&pio 6 11 GPIO_ACTIVE_LOW>;
	backlight = <&pwm_bl>;
	spi-max-frequency = <100000>;
	spi-cpol;
	spi-cpha;

	port {
		panel_input: endpoint {
			remote-endpoint = <&tcon0_out_panel>;
		};
	};
};
