tests: adc: add configuration and overlay for DMA support on Silabs IADC

This commit introduces a new configuration file for DMA support specific
to the Silabs IADC, along with updates to the test case YAML and device
tree overlay for the xg29_rb4412a board. The changes ensure that the ADC
driver can utilize DMA operations effectively.

Signed-off-by: Martin Hoff <[email protected]>

Author: Martinhoff-maker

tests/drivers/adc/adc_api/boards/xg29_rb4412a.overlay

@@ -16,6 +16,7 @@
 	status = "okay";
 	#address-cells = <1>;
 	#size-cells = <0>;
+	dmas = <&dma0 DMA_REQSEL_IADC0IADC_SCAN>;
 
 	channel@0 {
 		reg = <0>;
@@ -35,3 +36,7 @@
 		zephyr,input-positive = <IADC_INPUT_VBAT>;
 	};
 };
+
+&dma0 {
+	status = "okay";
+};

tests/drivers/adc/adc_api/overlay-dma-silabs.conf

@@ -0,0 +1,9 @@
+#
+# Copyright (c) 2025 Silicon Laboratories Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+CONFIG_TEST_USERSPACE=n
+CONFIG_DMA=y
+CONFIG_ADC_SILABS_IADC_DMA=y

tests/drivers/adc/adc_api/testcase.yaml

@@ -84,3 +84,12 @@ tests:
       - dma
     platform_allow:
       - esp32s3_devkitc/esp32s3/procpu
+  drivers.adc.dma_silabs:
+    extra_args:
+      - DTC_OVERLAY_FILE="boards/xg29_rb4412a.overlay"
+      - EXTRA_CONF_FILE="overlay-dma-silabs.conf"
+    depends_on:
+      - adc
+      - dma
+    platform_allow:
+      - xg29_rb4412a