feature symfony#5028 Finish symfony#4308: Documentation for the new PropertyNormalizer (mnapoli, WouterJ)

This PR was merged into the 2.6 branch.

Discussion
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Finish symfony#4308: Documentation for the new PropertyNormalizer

Finishes symfony#4308

| Q | A
| --- | ---
| Doc fix? | no
| New docs? | yes (symfony/symfony#9708)
| Applies to | 2.6+
| Fixed tickets | symfony#4272

Commits
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3b96301 Applied comments
629c8ac Added line returns…
6868a19 Updated the rendering of the list
4815c4a Introduction about normalizers
421aa41 ref symfony#4272 Documentation for the new PropertyNormalizer introduced in symfony/symfony#9708

Author: weaverryan

components/serializer.rst

@@ -50,6 +50,12 @@ which Encoders and Normalizer are going to be available::
 
     $serializer = new Serializer($normalizers, $encoders);
 
+There are several normalizers available, e.g. the
+:class:`Symfony\\Component\\Serializer\\Normalizer\\GetSetMethodNormalizer` or
+the :class:`Symfony\\Component\\Serializer\\Normalizer\\PropertyNormalizer`.
+To read more about them, refer to the `Normalizers`_ section of this page. All
+the examples shown below use the ``GetSetMethodNormalizer``.
+
 Serializing an Object
 ---------------------
 
@@ -238,6 +244,28 @@ When serializing, you can set a callback to format a specific object property::
     $serializer->serialize($person, 'json');
     // Output: {"name":"cordoval", "age": 34, "createdAt": "2014-03-22T09:43:12-0500"}
 
+Normalizers
+-----------
+
+There are several types of normalizers available:
+
+:class:`Symfony\\Component\\Serializer\\Normalizer\\GetSetMethodNormalizer`
+    This normalizer reads the content of the class by calling the "getters"
+    (public methods starting with "get"). It will denormalize data by calling
+    the constructor and the "setters" (public methods starting with "set").
+
+    Objects are serialized to a map of property names (method name stripped of
+    the "get" prefix and converted to lower case) to property values.
+
+:class:`Symfony\\Component\\Serializer\\Normalizer\\PropertyNormalizer`
+    This normalizer directly reads and writes public properties as well as
+    **private and protected** properties. Objects are normalized to a map of
+    property names to property values.
+
+.. versionadded:: 2.6 The
+    :class:`Symfony\\Component\\Serializer\\Normalizer\\PropertyNormalizer`
+    class was introduced in Symfony 2.6.
+
 Handling Circular References
 ----------------------------