diff --git a/Doc/tools/extensions/pyspecific.py b/Doc/tools/extensions/pyspecific.py
index 90d7cea..4df292d 100644
--- a/Doc/tools/extensions/pyspecific.py
+++ b/Doc/tools/extensions/pyspecific.py
@@ -131,6 +131,25 @@
         return [pnode]
 
 
+# Support for documenting platform availability
+
+class Availability(Directive):
+
+    has_content = False
+    required_arguments = 1
+    optional_arguments = 0
+    final_argument_whitespace = True
+
+    def run(self):
+        pnode = nodes.paragraph(classes=['availability'])
+        n, m = self.state.inline_text(':ref:`Availability <availability>`: ',
+                                      self.lineno)
+        pnode.extend(n + m)
+        n, m = self.state.inline_text(self.arguments[0], self.lineno)
+        pnode.extend(n + m)
+        return [pnode]
+
+
 # Support for documenting decorators
 
 class PyDecoratorMixin(object):
@@ -401,6 +420,7 @@
     app.add_role('issue', issue_role)
     app.add_role('source', source_role)
     app.add_directive('impl-detail', ImplementationDetail)
+    app.add_directive('availability', Availability)
     app.add_directive('deprecated-removed', DeprecatedRemoved)
     app.add_builder(PydocTopicsBuilder)
     app.add_builder(suspicious.CheckSuspiciousMarkupBuilder)
diff --git a/Doc/tools/rstlint.py b/Doc/tools/rstlint.py
index 2c1816e..a3024d6 100755
--- a/Doc/tools/rstlint.py
+++ b/Doc/tools/rstlint.py
@@ -27,17 +27,18 @@
     'table', 'target-notes', 'tip', 'title', 'topic', 'unicode', 'warning',
     # Sphinx and Python docs custom ones
     'acks', 'attribute', 'autoattribute', 'autoclass', 'autodata',
-    'autoexception', 'autofunction', 'automethod', 'automodule', 'centered',
-    'cfunction', 'class', 'classmethod', 'cmacro', 'cmdoption', 'cmember',
-    'code-block', 'confval', 'cssclass', 'ctype', 'currentmodule', 'cvar',
-    'data', 'decorator', 'decoratormethod', 'deprecated-removed',
-    'deprecated(?!-removed)', 'describe', 'directive', 'doctest', 'envvar',
-    'event', 'exception', 'function', 'glossary', 'highlight', 'highlightlang',
-    'impl-detail', 'index', 'literalinclude', 'method', 'miscnews', 'module',
-    'moduleauthor', 'opcode', 'pdbcommand', 'productionlist',
-    'program', 'role', 'sectionauthor', 'seealso', 'sourcecode', 'staticmethod',
-    'tabularcolumns', 'testcode', 'testoutput', 'testsetup', 'toctree', 'todo',
-    'todolist', 'versionadded', 'versionchanged'
+    'autoexception', 'autofunction', 'automethod', 'automodule',
+    'availability', 'centered', 'cfunction', 'class', 'classmethod', 'cmacro',
+    'cmdoption', 'cmember', 'code-block', 'confval', 'cssclass', 'ctype',
+    'currentmodule', 'cvar', 'data', 'decorator', 'decoratormethod',
+    'deprecated-removed', 'deprecated(?!-removed)', 'describe', 'directive',
+    'doctest', 'envvar', 'event', 'exception', 'function', 'glossary',
+    'highlight', 'highlightlang', 'impl-detail', 'index', 'literalinclude',
+    'method', 'miscnews', 'module', 'moduleauthor', 'opcode', 'pdbcommand',
+    'productionlist', 'program', 'role', 'sectionauthor', 'seealso',
+    'sourcecode', 'staticmethod', 'tabularcolumns', 'testcode', 'testoutput',
+    'testsetup', 'toctree', 'todo', 'todolist', 'versionadded',
+    'versionchanged'
 ]
 
 all_directives = '(' + '|'.join(directives) + ')'