docs: Document esp module for ESP8266.

I document as much as I could guess from experiments and reading the
code for the ``esp`` module for the ESP8266 port of Micropython.

For now the tag has to be set manually with -t option when building,
when we have properly split documentation, there will be a separate
config file for esp8266 with that the tag "port_esp8266" set.

To build use:

make SPHINXOPTS="-t port_esp8266" html

1 files changed, 56 insertions, 0 deletions

diff --git a/docs/library/esp.rst b/docs/library/esp.rst
new file mode 100644
index 0000000000..8dd39f536f
--- /dev/null
+++ b/docs/library/esp.rst
@@ -0,0 +1,56 @@
+:mod:`esp` --- functions related to the ESP8266
+===============================================
+
+.. module:: esp
+    :synopsis: functions related to the ESP8266
+
+The ``esp`` module contains specific functions related to the ESP8266 module.
+
+
+Functions
+---------
+
+.. function:: connect(ssid, password)
+
+    Connect to the specified wireless network, using the specified password.
+
+.. function:: disconnect()
+
+    Disconnect from the currently connected wireless network.
+
+.. function:: scan(cb)
+
+    Initiate scanning for the available wireless networks.
+
+    Once the scanning is complete, the provided callback function ``cb`` will
+    be called once for each network found, and passed a tuple with information
+    about that network.
+
+.. function:: status()
+
+    Return the current status of the wireless connection.
+
+    The possible statuses are defined as constants:
+
+        * ``STAT_IDLE`` -- no connection and no activity,
+        * ``STAT_CONNECTING`` -- connecting in progress,
+        * ``STAT_WRONG_PASSWORD`` -- failed due to incorrect password,
+        * ``STAT_NO_AP_FOUND`` -- failed because no access point replied,
+        * ``STAT_CONNECT_FAIL`` -- failed due to other problems,
+        * ``STAT_GOT_IP`` -- connection susccessful.
+
+.. function:: getaddrinfo((hostname, port, lambda))
+
+    Initiate resolving of the given hostname.
+
+    When the hostname is resolved, the provided ``lambda`` callback will be
+    called with two arguments, first being the hostname being resolved,
+    second a tuple with information about that hostname.
+
+Classes
+-------
+
+.. toctree::
+    :maxdepth: 1
+
+    esp.socket.rst