add policy constraints class
diff --git a/docs/x509/reference.rst b/docs/x509/reference.rst
index 8bb3f40..14fc37c 100644
--- a/docs/x509/reference.rst
+++ b/docs/x509/reference.rst
@@ -1860,6 +1860,40 @@
:type: int
+.. class:: PolicyConstraints
+
+ .. versionadded:: 1.3
+
+ The policy constraints extension can be used in certificates issued
+ to CAs. The policy constraints extension constrains path validation
+ in two ways. It can be used to prohibit policy mapping or require
+ that each certificate in a path contain an acceptable policy
+ identifier. For more information about the use of this extension see
+ :rfc:`5280`.
+
+ .. attribute:: require_explicit_policy
+
+ :type: int or None
+
+ If this field is present, the value indicates the number of additional
+ certificates that may appear in the path before an explicit policy is
+ required for the entire path. When an explicit policy is required, it
+ is necessary for all certificates in the path to contain an acceptable
+ policy identifier in the certificate policies extension. An
+ acceptable policy identifier is the identifier of a policy required
+ by the user of the certification path or the identifier of a policy
+ that has been declared equivalent through policy mapping.
+
+ .. attribute:: inhibit_policy_mapping
+
+ :type: int or None
+
+ If this field is present, the value indicates the number of additional
+ certificates that may appear in the path before policy mapping is no
+ longer permitted. For example, a value of one indicates that policy
+ mapping may be processed in certificates issued by the subject of this
+ certificate, but not in additional certificates in the path.
+
.. class:: CRLNumber(crl_number)
.. versionadded:: 1.2
@@ -2392,6 +2426,12 @@
the ``CRLNumber`` extension type. This extension only has meaning
for certificate revocation lists.
+ .. attribute:: POLICY_CONSTRAINTS
+
+ Corresponds to the dotted string ``"2.5.29.36"``. The identifier for the
+ :class:`PolicyConstraints` extension type.
+
+
.. class:: CRLEntryExtensionOID
.. versionadded:: 1.2