Certain NICs (e.g Mellanox) support additional hardware offloading when in switchdev mode instead of legacy mode.

this can be enabled with
devlink dev eswitch set pci/0000:03:00.0 mode switchdev
or disabled with
devlink dev eswitch set pci/0000:03:00.0 mode legacy

Proposed config option:

set interfaces ethernet eth0 switchdev