include: adc: add doxygen docs for voltage_divider extended API

Adds doxygen documentation for the extended API of the voltage divider ADC
driver.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

Author: kartben

dts/bindings/iio/afe/voltage-divider.yaml

@@ -1,6 +1,8 @@
 # Copyright (c) 2019, Peter Bigot Consulting, LLC
 # SPDX-License-Identifier: Apache-2.0
 
+title: Voltage Divider
+
 description: |
     Description for a voltage divider, with optional ability to measure
     resistance of the upper leg.

include/zephyr/drivers/adc/voltage_divider.h

@@ -4,14 +4,37 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+/**
+ * @file
+ * @brief Header file for extended API of Voltage Divider
+ * @ingroup adc_voltage_divider_interface
+ */
+
 #ifndef ZEPHYR_INCLUDE_DRIVERS_ADC_VOLTAGE_DIVIDER_H_
 #define ZEPHYR_INCLUDE_DRIVERS_ADC_VOLTAGE_DIVIDER_H_
 
 #include <zephyr/drivers/adc.h>
 
+/**
+ * @brief Voltage Divider
+ * @defgroup adc_voltage_divider_interface Voltage Divider
+ * @ingroup adc_interface_ext
+ * @{
+ */
+
+/**
+ * @brief Voltage divider DT struct.
+ *
+ * This stores information about a voltage divider obtained from Devicetree.
+ *
+ * @see VOLTAGE_DIVIDER_DT_SPEC_GET
+ */
 struct voltage_divider_dt_spec {
+	/** ADC channel info */
 	const struct adc_dt_spec port;
+	/** Full resistance in ohms */
 	uint32_t full_ohms;
+	/** Output resistance in ohms */
 	uint32_t output_ohms;
 };
 
@@ -33,7 +56,7 @@ struct voltage_divider_dt_spec {
 	}
 
 /**
- * @brief Calculates the actual voltage from the measured voltage
+ * @brief Calculates the actual voltage from a measured voltage
  *
  * @param[in] spec voltage divider specification from Devicetree.
  * @param[in,out] v_to_v Pointer to the measured voltage on input, and the
@@ -56,4 +79,6 @@ static inline int voltage_divider_scale_dt(const struct voltage_divider_dt_spec
 	return 0;
 }
 
+/** @} */
+
 #endif /* ZEPHYR_INCLUDE_DRIVERS_ADC_VOLTAGE_DIVIDER_H_ */