add UnrecognizedExtension class
diff --git a/docs/x509/reference.rst b/docs/x509/reference.rst
index bbea490..14727e7 100644
--- a/docs/x509/reference.rst
+++ b/docs/x509/reference.rst
@@ -1880,6 +1880,27 @@
:type: int
+.. class:: UnrecognizedExtension
+
+ .. versionadded:: 1.2
+
+ A generic extension class used to hold the raw value of **non-critical**
+ extensions that ``cryptography`` does not know how to parse. Extensions
+ marked critical will still raise
+ :class:`~cryptography.x509.UnsupportedExtension`.
+
+ .. attribute:: oid
+
+ :type: :class:`ObjectIdentifier`
+
+ Returns the OID associated with this extension.
+
+ .. attribute:: value
+
+ :type: byte
+
+ Returns the DER encoded bytes payload of the extension.
+
.. class:: CertificatePolicies(policies)
.. versionadded:: 0.9