docs/system: add basic virtio-snd documentation

This commit adds basic documentation for using virtio-snd.

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <e7fb941cf7636fdff40cbdcdcd660dec5f15ca3c.1698062525.git.manos.pitsidianakis@linaro.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index c09bb8c..4fad272 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2317,6 +2317,7 @@
 F: hw/audio/virtio-snd.c
 F: hw/audio/virtio-snd-pci.c
 F: include/hw/audio/virtio-snd.h
+F: docs/system/devices/virtio-snd.rst
 
 nvme
 M: Keith Busch <kbusch@kernel.org>