docs: Add missing peripheral driver docs (ADC, DAC, RTC I/O, I2S)

docs/api/peripherals/adc.rst

@@ -0,0 +1,62 @@
+Analog to Digital Converter
+===========================
+
+Overview
+--------
+
+ESP32 integrates two 12-bit SAR ("Successive Approximation Register") ADCs (Analog to Digital Converters) and supports measurements on 18 channels (analog enabled pins). Some of these pins can be used to build a programmable gain amplifier which is used for the measurement of small
+analog signals.
+
+The ADC driver API currently only supports ADC1 (9 channels, attached to GPIOs 32-39).
+
+Taking an ADC reading involves configuring the ADC with the desired precision and attentuation settings, and then calling adc1_get_voltage() to read the channel.
+
+It is also possible to read the internal hall effect sensor via ADC1.
+
+Application Example
+-------------------
+
+Reading voltage on ADC1 channel 0 (GPIO 36)::
+
+    #include <driver/adc.h>
+
+    ...
+
+        adc1_config_width(ADC_WIDTH_12Bit);
+        adc1_config_channel_atten(ADC1_CHANNEL_0,ADC_ATTEN_0db);
+        int val = adc1_get_voltage(ADC1_CHANNEL_0);
+
+Reading the internal hall effect sensor::
+
+    #include <driver/adc.h>
+
+    ...
+
+        adc1_config_width(ADC_WIDTH_12Bit);
+        int val = hall_sensor_read();
+
+The value read in both these examples is 12 bits wide (range 0-4095).
+
+API Reference
+-------------
+
+Header Files
+^^^^^^^^^^^^
+
+  * `components/driver/include/driver/adc.h`
+
+Enumerations
+^^^^^^^^^^^^
+
+  .. doxygenenum:: adc1_channel_t
+  .. doxygenenum:: adc_atten_t
+  .. doxygenenum:: adc_bits_width_t
+
+Functions
+^^^^^^^^^
+
+  .. doxygenfunction:: adc1_config_width
+  .. doxygenfunction:: adc1_config_channel_atten
+  .. doxygenfunction:: adc1_get_voltage
+  .. doxygenfunction:: hall_sensor_read
+