samples: drivers: adc: adc_dt: Add overlay for xg24_rb4187c

Add support for xg24_rb4187c to the ADC sample app. Configure two
channels, one measuring the AVDD supply against the 1.21V bandgap
reference, and one measuring pin PB1 (wired to button 0) against
the AVDD (VDDX) reference.

Signed-off-by: Aksel Skauge Mellbye <aksel.mellbye@silabs.com>

samples/drivers/adc/adc_dt/boards/xg24_rb4187c.overlay

@@ -0,0 +1,50 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Copyright (c) 2025 Silicon Laboratories Inc.
+ */
+
+#include <dt-bindings/pinctrl/silabs/xg24-pinctrl.h>
+#include <dt-bindings/adc/silabs-adc.h>
+
+/ {
+	zephyr,user {
+		io-channels = <&adc0 3>, <&adc0 4>;
+	};
+};
+
+&pinctrl {
+	adc0_default: adc0_default {
+		group0 {
+			/* Allocate odd bus 0 on GPIO port B to IADC for access to pin PB1 */
+			silabs,analog-bus = <ABUS_BODD0_IADC0>;
+		};
+	};
+};
+
+&adc0 {
+	pinctrl-0 = <&adc0_default>;
+	pinctrl-names = "default";
+	#address-cells = <1>;
+	#size-cells = <0>;
+	status = "okay";
+
+	channel@3 {
+		reg = <3>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <12>;
+		zephyr,input-positive = <IADC_INPUT_AVDD>;
+	};
+
+	channel@4 {
+		reg = <4>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_VDD_1";
+		zephyr,vref-mv = <3300>;
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <12>;
+		zephyr,input-positive = <IADC_INPUT_PB1>;
+	};
+};

samples/drivers/adc/adc_dt/sample.yaml

@@ -35,6 +35,7 @@ tests:
       - frdm_mcxn947/mcxn947/cpu0
       - frdm_mcxc242
       - ucans32k1sic
+      - xg24_rb4187c
     integration_platforms:
       - nucleo_l073rz
       - nrf52840dk/nrf52840