docs: add some documentation dirs to the driver-api book

Those are subsystem docs, with a mix of kABI and user-faced
docs. While they're not split, keep the dirs where they are,
adding just a pointer to the main index.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
diff --git a/Documentation/index.rst b/Documentation/index.rst
index a322c87..dcdaaff 100644
--- a/Documentation/index.rst
+++ b/Documentation/index.rst
@@ -92,6 +92,10 @@
 
    driver-api/index
    core-api/index
+   accounting/index
+   block/index
+   hid/index
+   iio/index
    leds/index
    media/index
    networking/index