asyncio: document the new asyncio.subprocess module
diff --git a/Doc/library/asyncio.rst b/Doc/library/asyncio.rst
index 9787f19..542f476 100644
--- a/Doc/library/asyncio.rst
+++ b/Doc/library/asyncio.rst
@@ -48,6 +48,7 @@
    asyncio-task.rst
    asyncio-protocol.rst
    asyncio-stream.rst
+   asyncio-subprocess.rst
    asyncio-sync.rst
    asyncio-dev.rst