Adding a section to the FAQ about array notation. (#30782)

* Adding a section to the FAQ about array notation.

* Fixing spelling of jinja and Celsius.

* Adding an example that uses dots.

docs/docsite/rst/faq.rst

@@ -305,6 +305,20 @@ You shouldn't put plaintext passwords in your playbook or host_vars; instead, us
 
 .. _commercial_support:
 
+Ansible supports dot notation and array notation for variables. Which notation should I use?
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+
+The dot notation comes from Jinja and works fine for variables without special
+characters. If your variable contains dots (.), colons (:), or dashes (-) it is
+safer to use the array notation for variables.
+
+.. code-block:: jinja
+
+    item[0]['checksum:md5']
+    item['section']['2.1']
+    item['region']['Mid-Atlantic']
+    It is {{ temperature['Celsius']['-3'] }} outside.
+
 Can I get training on Ansible?
 ++++++++++++++++++++++++++++++
 
@@ -407,6 +421,3 @@ Please see the section below for a link to IRC and the Google Group, where you c
        Have a question?  Stop by the google group!
    `irc.freenode.net <http://irc.freenode.net>`_
        #ansible IRC chat channel
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