arm64: dts: mediatek: asurada: Add display backlight

Add the display backlight for the Asurada platform. It relies on the
display PWM controller, so also enable and configure this component.
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://lore.kernel.org/r/20221102190611.283546-3-nfraprado@collabora.comSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>

arch/arm64/boot/dts/mediatek/mt8192-asurada.dtsi

@@ -23,6 +23,16 @@ memory@40000000 {
 		reg = <0 0x40000000 0 0x80000000>;
 	};
 
+	backlight_lcd0: backlight-lcd0 {
+		compatible = "pwm-backlight";
+		pwms = <&pwm0 0 500000>;
+		power-supply = <&ppvar_sys>;
+		enable-gpios = <&pio 152 0>;
+		brightness-levels = <0 1023>;
+		num-interpolated-steps = <1023>;
+		default-brightness-level = <576>;
+	};
+
 	pp1000_dpbrdg: regulator-1v0-dpbrdg {
 		compatible = "regulator-fixed";
 		regulator-name = "pp1000_dpbrdg";
@@ -838,6 +848,17 @@ pins-pcie-en-pp3300-wlan {
 		};
 	};
 
+	pwm0_pins: pwm0-default-pins {
+		pins-pwm {
+			pinmux = <PINMUX_GPIO40__FUNC_DISP_PWM>;
+		};
+
+		pins-inhibit {
+			pinmux = <PINMUX_GPIO152__FUNC_GPIO152>;
+			output-high;
+		};
+	};
+
 	scp_pins: scp-pins {
 		pins-vreq-vao {
 			pinmux = <PINMUX_GPIO195__FUNC_SCP_VREQ_VAO>;
@@ -899,6 +920,13 @@ &pmic {
 	interrupts-extended = <&pio 214 IRQ_TYPE_LEVEL_HIGH>;
 };
 
+&pwm0 {
+	status = "okay";
+
+	pinctrl-names = "default";
+	pinctrl-0 = <&pwm0_pins>;
+};
+
 &scp {
 	status = "okay";