Add documentation.

Change-Id: I8197ec2e52596fa4136f8af9aa93ea06e56d4d0d
diff --git a/doc/source/index.rst b/doc/source/index.rst
new file mode 100644
index 0000000..f901fd0
--- /dev/null
+++ b/doc/source/index.rst
@@ -0,0 +1,32 @@
+.. Zuul documentation master file, created by
+   sphinx-quickstart on Fri Jun  8 14:44:26 2012.
+   You can adapt this file completely to your liking, but it should at least
+   contain the root `toctree` directive.
+
+Zuul - A Project Gating System
+==============================
+
+Zuul is a program that is used to gate the source code repository of a
+project so that changes are only merged if they pass tests.
+
+The main component of Zuul is the scheduler.  It receives events
+related to proposed changes (currently from Gerrit), triggers tests
+based on those events (currently on Jenkins), and reports back.
+
+Contents:
+
+.. toctree::
+   :maxdepth: 2
+
+   gating
+   triggers
+   launchers
+   zuul
+
+Indices and tables
+==================
+
+* :ref:`genindex`
+* :ref:`modindex`
+* :ref:`search`
+