What I think is the least intrusive and allows for maximum flexibility
is having the VLAN bridge filtering depend on VLAN support (CONFIG_VLAN_8021Q).
There already is drivers that depend on that value to enable filtering.
And make the support of VLAN filtering in the bridge conditional like
IGMP snooping is optional
--- a/net/bridge/Kconfig
+++ b/net/bridge/Kconfig
@@ -46,3 +46,17 @@ config BRIDGE_IGMP_SNOOPING
Say N to exclude this support and reduce the binary size.
If unsure, say Y.
+
+config BRIDGE_VLAN_FILTERING
+ bool "VLAN filtering"
+ depends on BRIDGE
+ depends on VLAN_8021Q
+ default n
+ ---help---
+ If you say Y here, then the Ethernet bridge will be able to
+ selectively filter traffic based on VLAN tag.
+
+ Say N to exclude this support and reduce the binary size.
+
+ If unsure, say Y.
