docs/library: Add documentation for esp32 module.

docs/library/esp32.rst

+:mod:`esp32` --- functionality specific to the ESP32
+====================================================
+
+.. module:: esp32
+    :synopsis: functionality specific to the ESP32
+
+The ``esp32`` module contains functions and classes specifically aimed at
+controlling ESP32 modules.
+
+
+Functions
+---------
+
+.. function:: wake_on_touch(wake)
+
+    Configure whether or not a touch will wake the device from sleep.
+    *wake* should be a boolean value.
+
+.. function:: wake_on_ext0(pin, level)
+
+    Configure how EXT0 wakes the device from sleep.  *pin* can be ``None``
+    or a valid Pin object.  *level* should be ``esp32.WAKEUP_ALL_LOW`` or
+    ``esp32.WAKEUP_ANY_HIGH``.
+
+.. function:: wake_on_ext1(pins, level)
+
+    Configure how EXT1 wakes the device from sleep.  *pins* can be ``None``
+    or a tuple/list of valid Pin objects.  *level* should be ``esp32.WAKEUP_ALL_LOW``
+    or ``esp32.WAKEUP_ANY_HIGH``.
+
+.. function:: raw_temperature()
+
+    Read the raw value of the internal temperature sensor, returning an integer.
+
+.. function:: hall_sensor()
+
+    Read the raw value of the internal Hall sensor, returning an integer.
+
+
+The Ultra-Low-Power co-processor
+--------------------------------
+
+.. class:: ULP()
+
+    This class provides access to the Ultra-Low-Power co-processor.
+
+.. method:: ULP.set_wakeup_period(period_index, period_us)
+
+    Set the wake-up period.
+
+.. method:: ULP.load_binary(load_addr, program_binary)
+
+    Load a *program_binary* into the ULP at the given *load_addr*.
+
+.. method:: ULP.run(entry_point)
+
+    Start the ULP running at the given *entry_point*.
+
+
+Constants
+---------
+
+.. data:: esp32.WAKEUP_ALL_LOW
+          esp32.WAKEUP_ANY_HIGH
+
+   Selects the wake level for pins.

docs/library/index.rst

@@ -148,3 +148,4 @@ The following libraries are specific to the ESP8266 and ESP32.
   :maxdepth: 2
 
   esp.rst
+  esp32.rst