arm64: dts: salvator-x: Add panel backlight support

The panel backlight is controlled through a GPIO and a PWM channel.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
[simon: apply to salvator-x.dtsi instead of r8a7795-salvator-x.dts]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/salvator-x.dtsi

@@ -58,6 +58,16 @@ audio_clkout: audio_clkout {
 		clock-frequency = <11289600>;
 	};
 
+	backlight: backlight {
+		compatible = "pwm-backlight";
+		pwms = <&pwm1 0 50000>;
+
+		brightness-levels = <256 128 64 16 8 4 0>;
+		default-brightness-level = <6>;
+
+		enable-gpios = <&gpio6 7 GPIO_ACTIVE_HIGH>;
+	};
+
 	reg_1p8v: regulator0 {
 		compatible = "regulator-fixed";
 		regulator-name = "fixed-1.8V";
@@ -358,6 +368,11 @@ i2c2_pins: i2c2 {
 		function = "i2c2";
 	};
 
+	pwm1_pins: pwm {
+		groups = "pwm1_a";
+		function = "pwm1";
+	};
+
 	scif1_pins: scif1 {
 		groups = "scif1_data_a", "scif1_ctrl";
 		function = "scif1";
@@ -443,6 +458,13 @@ pwen {
 	};
 };
 
+&pwm1 {
+	pinctrl-0 = <&pwm1_pins>;
+	pinctrl-names = "default";
+
+	status = "okay";
+};
+
 &rcar_sound {
 	pinctrl-0 = <&sound_pins &sound_clk_pins>;
 	pinctrl-names = "default";