net: Introduce L3 Master device abstraction

L3 master devices allow users of the abstraction to influence FIB lookups
for enslaved devices. Current API provides a means for the master device
to return a specific FIB table for an enslaved device, to return an
rtable/custom dst and influence the OIF used for fib lookups.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/l3mdev/Kconfig b/net/l3mdev/Kconfig
new file mode 100644
index 0000000..5d47325
--- /dev/null
+++ b/net/l3mdev/Kconfig
@@ -0,0 +1,10 @@
+#
+# Configuration for L3 master device support
+#
+
+config NET_L3_MASTER_DEV
+	bool "L3 Master device support"
+	depends on INET || IPV6
+	---help---
+	  This module provides glue between core networking code and device
+	  drivers to support L3 master devices like VRF.