Input: docs - update joystick documentation a bit

Consolidate use instructions and userspace API notes into the same chapter;
remove completely obsolete references, move into a separate subdirectory.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
diff --git a/Documentation/input/index.rst b/Documentation/input/index.rst
index 5887c79..b25a671 100644
--- a/Documentation/input/index.rst
+++ b/Documentation/input/index.rst
@@ -2,8 +2,7 @@
 The Linux Input Documentation
 =============================
 
-Core API
-========
+Contents:
 
 .. toctree::
    :maxdepth: 2
@@ -12,8 +11,7 @@
    input
    input-programming
    event-codes
-   joystick
-   joystick-api
+   joydev/index
    multi-touch-protocol
    gamepad
    gameport-programming