vhost: Add event index for interrupt notification to driver

VPP only supports a poor man's approach for interrupt notification to the
driver. It uses a simple binary flag for "interrupt needed" or "interrupt
not needed". Most drivers support more sophisticated event index already.
This feature is to add the long due missing feature and make it configurable,
off by default.

Type: feature

Signed-off-by: Steven Luong <sluong@cisco.com>
Change-Id: I68dab7dd07045cafb49af97b7f70db9b8131ae03
diff --git a/MAINTAINERS b/MAINTAINERS
index a3d582f..d99bc4c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -113,6 +113,12 @@
 M:	Mohsin Kazmi <sykazmi@cisco.com>
 F:	src/vnet/devices/tap/
 
+VNET Vhost User Driver
+I:	vhost
+Y:	src/vnet/devices/virtio/FEATURE.yaml
+M:	Steven Luong <sluong@cisco.com>
+F:	src/vnet/devices/virtio/vhost_user*
+
 VNET Native Virtio Drivers
 I:	virtio
 Y:	src/vnet/devices/virtio/FEATURE.yaml