Linux support for network switch chips has been difficult for router systems.
Routers would like to present the switch interfaces as standard linux network interfaces, but the model doesn't quite fit. Linux models a MAC and Phy as an interface. Switches generally have a mix of MACs and Phys.
Openwrt has it's own solution using swconfig, which provides an API for controlling a switch. It maps interfaces using VLANs.
Marvell has provided a more integrated solution called Distributed Switch Architecture. This has been accepted into the kernel and is being expanded to other manufacturers switch chips.