arm64: dts: rockchip: add ADC buttons to rk3588-evb1

The Rockchip EVB1 has a couple of buttons connected via an ADC
line. Let's add them to its devicetree.
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20231005134357.37171-1-sebastian.reichel@collabora.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3588-evb1-v10.dts

@@ -7,6 +7,7 @@
 /dts-v1/;
 
 #include <dt-bindings/gpio/gpio.h>
+#include <dt-bindings/input/input.h>
 #include <dt-bindings/pinctrl/rockchip.h>
 #include "rk3588.dtsi"
 
@@ -23,6 +24,38 @@ chosen {
 		stdout-path = "serial2:1500000n8";
 	};
 
+	adc-keys {
+		compatible = "adc-keys";
+		io-channels = <&saradc 1>;
+		io-channel-names = "buttons";
+		keyup-threshold-microvolt = <1800000>;
+		poll-interval = <100>;
+
+		button-vol-up {
+			label = "Volume Up";
+			linux,code = <KEY_VOLUMEUP>;
+			press-threshold-microvolt = <17000>;
+		};
+
+		button-vol-down {
+			label = "Volume Down";
+			linux,code = <KEY_VOLUMEDOWN>;
+			press-threshold-microvolt = <417000>;
+		};
+
+		button-menu {
+			label = "Menu";
+			linux,code = <KEY_MENU>;
+			press-threshold-microvolt = <890000>;
+		};
+
+		button-escape {
+			label = "Escape";
+			linux,code = <KEY_ESC>;
+			press-threshold-microvolt = <1235000>;
+		};
+	};
+
 	backlight: backlight {
 		compatible = "pwm-backlight";
 		power-supply = <&vcc12v_dcin>;
@@ -286,6 +319,11 @@ &pwm2 {
 	status = "okay";
 };
 
+&saradc {
+	vref-supply = <&vcc_1v8_s0>;
+	status = "okay";
+};
+
 &sdhci {
 	bus-width = <8>;
 	no-sdio;