net: dsa: initial MT7628 tagging driver

Add support for the MT7628 embedded switch's tag.

The MT7628 tag is merged with the VLAN TPID field when a VLAN is
appended by the switch hardware. It is not installed if the VLAN tag is
already there on ingress. Due to this hardware quirk the tag cannot be
trusted for port 0 if we don't know that the VLAN was added by the
hardware. As a workaround for this the switch is configured to always
append the port PVID tag even if the incoming packet is already tagged.
The tagging driver can then trust that the tag is always accurate and
the whole VLAN tag can be removed on ingress as it's only metadata for
the tagger.

On egress the MT7628 tag allows precise TX, but the correct VLAN tag
from tag_8021q is still appended or the switch will not forward the
packet.

Signed-off-by: Joris Vaisvila <joey@tinyisr.com>
Link: https://patch.msgid.link/20260813190241.789323-4-joey@tinyisr.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

0 files changed, 0 insertions, 0 deletions