samples: adc: siwx91x: Add adc_dt support for siwx917_rb4338a

Add an overlay to enable the adc_dt sample on the siwx917_rb4338a
board.

Signed-off-by: Sai Santhosh Malae <[email protected]>
(cherry picked from commit ef1bd9d)
Upstream-status: available

Author: smalae

samples/drivers/adc/adc_dt/boards/siwx917_rb4338a.overlay

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2025 Silicon Laboratories Inc.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	zephyr,user {
+		io-channels = <&adc0 0>;
+	};
+};
+
+&pinctrl0 {
+	adc0_default: adc0_default {
+		group {
+			pinmux = <AGPIO_ULP1>;
+		};
+	};
+};
+
+&adc0 {
+	pinctrl-0 = <&adc0_default>;
+	pinctrl-names = "default";
+	silabs,adc-ref-voltage = <3300>;
+
+	channel@0 {
+		reg = <0>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <0>;
+		zephyr,resolution = <12>;
+		zephyr,input-positive = <10>;
+	};
+	status = "okay";
+};