DOC: [ArrowStringArray] release note and other documentation

doc/source/whatsnew/v1.3.0.rst

@@ -134,6 +134,56 @@ a copy will no longer be made (:issue:`32960`)
 The default behavior when not passing ``copy`` will remain unchanged, i.e.
 a copy will be made.
 
+.. _whatsnew_130.arrow_string:
+
+PyArrow backed string data type
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+We've enhanced the :class:`StringDtype`, an extension type dedicated to string data.
+(:issue:`39908`)
+
+It is now possible to specify a ``storage`` keyword option to :class:`StringDtype`, use
+pandas options or specify the dtype using ``dtype='string[pyarrow]'``
+
+.. warning::
+
+   ``string[pyarrow]`` is currently considered experimental. The implementation
+   and parts of the API may change without warning.
+
+The ``'string[pyarrow]'`` extension type solves several issues with NumPy backed arrays:
+
+1. 
+2. 
+3. 
+
+
+.. ipython:: python
+
+   pd.Series(['abc', None, 'def'], dtype=pd.StringDtype(storage="pyarrow"))
+
+You can use the alias ``"string[pyarrow]"`` as well.
+
+.. ipython:: python
+
+   s = pd.Series(['abc', None, 'def'], dtype="string[pyarrow]")
+   s
+
+The usual string accessor methods work. Where appropriate, the return type
+of the Series or columns of a DataFrame will also have string dtype.
+
+.. ipython:: python
+
+   s.str.upper()
+   s.str.split('b', expand=True).dtypes
+
+String accessor methods returning integers will return a value with :class:`Int64Dtype`
+
+.. ipython:: python
+
+   s.str.count("a")
+
+See :ref:`text.types` for more.
+
 .. _whatsnew_130.enhancements.other:
 
 Other enhancements