doc: Start improving our pytest documentation

Begin the work of documenting all of our pytests. To do this, we should
have a directory under develop for it as there will be a large number of
new files. As the current document is referenced externally in a number
of locations, add the sphinx_reredirects module so that we can redirect
from the old location to the new.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/conf.py b/doc/conf.py
index c50daf8..3cb9b2b 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -47,7 +47,8 @@
 extensions = ['kerneldoc', 'rstFlatTable', 'kernel_include',
               'kfigure', 'sphinx.ext.ifconfig', # 'automarkup',
               'maintainers_include', 'sphinx.ext.autosectionlabel',
-              'kernel_abi', 'kernel_feat', 'sphinx-prompt']
+              'kernel_abi', 'kernel_feat', 'sphinx-prompt',
+              'sphinx_reredirects' ]
 
 #
 # cdomain is badly broken in Sphinx 3+.  Leaving it out generates *most*
@@ -148,6 +149,11 @@
 copyright = 'The U-Boot development community'
 author = 'The U-Boot development community'
 
+# Pages we have moved after being heavily referenced externally
+redirects = {
+    "develop/py_testing": "pytest/usage.html"
+}
+
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
 # built documents.