drivers: adc: siwx91x: Add ref_internal to device API

The Siwx91x ADC reference voltage is configurable rather than fixed.
Expose `ref_internal` in the device API so the driver can retrieve the
reference voltage from the device tree instead of assuming a constant
value.

Signed-off-by: Sai Santhosh Malae <[email protected]>
(cherry picked from commit f4c152a)
Upstream-status: available

Author: smalae

drivers/adc/adc_silabs_siwx91x.c

@@ -378,13 +378,16 @@ static void adc_siwx91x_isr(const struct device *dev)
 	}
 }
 
-static DEVICE_API(adc, adc_siwx91x_driver_api) = {
-	.channel_setup = adc_siwx91x_channel_setup,
-	.read = adc_siwx91x_read,
-};
+#define ADC_SIWX91X_DRIVER_API(inst)                                                               \
+	static DEVICE_API(adc, adc_siwx91x_driver_api_##inst) = {                                  \
+		.channel_setup = adc_siwx91x_channel_setup,                                        \
+		.read = adc_siwx91x_read,                                                          \
+		.ref_internal = DT_INST_PROP(inst, silabs_adc_ref_voltage),                        \
+	};
 
 #define SIWX91X_ADC_INIT(inst)                                                                     \
 	PINCTRL_DT_INST_DEFINE(inst);                                                              \
+	ADC_SIWX91X_DRIVER_API(inst);                                                              \
                                                                                                    \
 	static struct adc_siwx91x_chan_data adc_chan_data_##inst[DT_CHILD_NUM(DT_DRV_INST(inst))]; \
                                                                                                    \
@@ -414,6 +417,7 @@ static DEVICE_API(adc, adc_siwx91x_driver_api) = {
 	};                                                                                         \
                                                                                                    \
 	DEVICE_DT_INST_DEFINE(inst, adc_siwx91x_init, NULL, &adc_data_##inst, &adc_cfg_##inst,     \
-			      PRE_KERNEL_1, CONFIG_ADC_INIT_PRIORITY, &adc_siwx91x_driver_api);
+			      PRE_KERNEL_1, CONFIG_ADC_INIT_PRIORITY,                              \
+			      &adc_siwx91x_driver_api_##inst);
 
 DT_INST_FOREACH_STATUS_OKAY(SIWX91X_ADC_INIT)