add interface docs for dsa_params_supported
diff --git a/docs/hazmat/backends/interfaces.rst b/docs/hazmat/backends/interfaces.rst
index 114b993..3b3d5ef 100644
--- a/docs/hazmat/backends/interfaces.rst
+++ b/docs/hazmat/backends/interfaces.rst
@@ -369,6 +369,15 @@
:returns: ``True`` if the specified ``algorithm`` is supported by this
backend, otherwise ``False``.
+ .. method:: dsa_parameters_supported(p, q):
+
+ :param int p: The p value of a DSA key.
+
+ :param int q: The q value of a DSA key.
+
+ :returns: ``True`` if the given values of ``p`` and ``q`` are supported
+ by this backend, otherwise ``False``.
+
.. class:: CMACBackend