When I run 'swconfig list' I see:-

root@OpenWrt:/# swconfig list
Found: switch1 - eth1
Found: switch0 - ag71xx-mdio.0

But all the references in /etc/config/network are to eth0.1, eth0.2 etc. 

How is switch0 supposed to be connected to eth0? (As in logically/programatically connected)

As it is nothing on switch0 actually works at present. (Mikrotik RB2011)