Mention pylibfdt in the documentation

Add a note about pylibfdt in the README.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

README

@@ -7,6 +7,53 @@ DTC and LIBFDT are maintained by:
 David Gibson <david@gibson.dropbear.id.au>
 Jon Loeliger <jdl@jdl.com>
 
+
+Python library
+--------------
+
+A Python library is also available. To build this you will need to install
+swig and Python development files. On Debian distributions:
+
+   sudo apt-get install swig python-dev
+
+The library provides an Fdt class which you can use like this:
+
+$ PYTHONPATH=../pylibfdt python
+>>> import libfdt
+>>> fdt = libfdt.Fdt(open('test_tree1.dtb').read())
+>>> node = fdt.path_offset('/subnode@1')
+>>> print node
+124
+>>> prop_offset = fdt.first_property_offset(node)
+>>> prop = fdt.get_property_by_offset(prop_offset)
+>>> print '%s=%r' % (prop.name, prop.value)
+compatible=bytearray(b'subnode1\x00')
+>>> print '%s=%s' % (prop.name, prop.value)
+compatible=subnode1
+>>> node2 = fdt.path_offset('/')
+>>> print fdt.getprop(node2, 'compatible')
+test_tree1
+
+You will find tests in tests/pylibfdt_tests.py showing how to use each
+method. Help is available using the Python help command, e.g.:
+
+    $ cd pylibfdt
+    $ python -c "import libfdt; help(libfdt)"
+
+If you add new features, please check code coverage:
+
+    $ sudo apt-get install python-pip python-pytest
+    $ sudo pip install coverage
+    $ cd tests
+    $ coverage run pylibfdt_tests.py
+    $ coverage html
+    # Open 'htmlcov/index.html' in your browser
+
+
+More work remains to support all of libfdt, including access to numeric
+values.
+
+
 Mailing list
 ------------
 The following list is for discussion about dtc and libfdt implementation