Docs: add admin reference section

Add an admin reference section and move some of the admin-specific
ref material there.

Also, split the drivers out to their own section so that it's easier
to find driver-specific material in the admin reference TOC.

Change-Id: Iabe342eb8cf7f5dfecb76a22338d366a3655ac38

doc/source/discussion/index.rst

@@ -14,6 +14,5 @@ configure it to meet your needs.
    concepts
    components
    gating
-   tenants
    encryption
    tenant-scoped-rest-api

doc/source/index.rst

@@ -34,6 +34,7 @@ Zuul Admins
 
    tutorials/admins/index
    howtos/admins/index
+   reference/admins/index
 
 Digging Deeper
 **************

doc/source/reference/admins/connections.rst

@@ -18,9 +18,9 @@ Connections
 
 In order to interact with external systems, Zuul must have a
 *connection* to that system configured.  Zuul includes a number of
-drivers, each of which implements the functionality necessary to
-connect to a system.  Each connection in Zuul is associated with a
-driver.
+:ref:`drivers <drivers>`, each of which implements the functionality
+necessary to connect to a system.  Each connection in Zuul is
+associated with a driver.
 
 To configure a connection in Zuul, select a unique name for the
 connection and add a section to ``zuul.conf`` with the form
@@ -41,33 +41,3 @@ for a given server, however, if you need more than one (for example,
 to satisfy unique reporting requirements) be sure to list the primary
 connection first as that is what Zuul will use to look up all changes
 for that server.
-
-.. _drivers:
-
-Drivers
--------
-
-Drivers may support any of the following functions:
-
-* Sources -- hosts git repositories for projects.  Zuul can clone git
-  repos for projects and fetch refs.
-* Triggers -- emits events to which Zuul may respond.  Triggers are
-  configured in pipelines to cause changes or other refs to be
-  enqueued.
-* Reporters -- outputs information when a pipeline is finished
-  processing an item.
-
-Zuul includes the following drivers:
-
-.. toctree::
-   :maxdepth: 2
-
-   drivers/gerrit
-   drivers/github
-   drivers/pagure
-   drivers/git
-   drivers/mqtt
-   drivers/smtp
-   drivers/sql
-   drivers/timer
-   drivers/zuul

doc/source/reference/admins/drivers/index.rst

@@ -0,0 +1,29 @@
+.. _drivers:
+
+Drivers
+=======
+
+Drivers may support any of the following functions:
+
+* Sources -- hosts git repositories for projects.  Zuul can clone git
+  repos for projects and fetch refs.
+* Triggers -- emits events to which Zuul may respond.  Triggers are
+  configured in pipelines to cause changes or other refs to be
+  enqueued.
+* Reporters -- outputs information when a pipeline is finished
+  processing an item.
+
+Zuul includes the following drivers:
+
+.. toctree::
+   :maxdepth: 2
+
+   gerrit
+   github
+   pagure
+   git
+   mqtt
+   smtp
+   sql
+   timer
+   zuul

doc/source/reference/admins/index.rst

@@ -0,0 +1,10 @@
+Admin Reference
+===============
+
+.. toctree::
+   :maxdepth: 3
+
+   tenants
+   connections
+   drivers/index
+   client

doc/source/reference/index.rst

@@ -4,8 +4,6 @@ Reference
 .. toctree::
    :maxdepth: 2
 
-   connections
-   client
    monitoring
    web
    developer/index