Add configuration documentation

This adds the start of v3 configuration documentation.

Change-Id: I3cc2f69c61795ef82d0e1c71d639e46fd1d5a7d1
Story: 2000790
Task: 3314
diff --git a/doc/source/admin-config.rst b/doc/source/admin-config.rst
new file mode 100644
index 0000000..03f742b
--- /dev/null
+++ b/doc/source/admin-config.rst
@@ -0,0 +1,24 @@
+:title: Administrative Configuration
+
+.. _admin-config:
+.. _drivers:
+
+Administrative Configuration
+============================
+
+TODO:
+
+* zuul.conf
+* connections
+
+* main.yaml
+* tenants
+* trusted/untrusted
+
+* drivers
+* gerrit
+  * trigger config
+  * reporter config
+* github
+  * trigger config
+  * reporter config