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/Makefile b/net/l3mdev/Makefile
new file mode 100644
index 0000000..84a53a6
--- /dev/null
+++ b/net/l3mdev/Makefile
@@ -0,0 +1,5 @@
+#
+# Makefile for the L3 device API
+#
+
+obj-$(CONFIG_NET_L3_MASTER_DEV) += l3mdev.o