Here is a typical /etc/config/network config file to setup a fonera as a bridge between the wired (eth0) and wireless (ath0) interfaces:
# Loopback
config interface loopback
option ifname "lo"
option proto static
option ipaddr 127.0.0.1
option netmask 255.0.0.0
# LAN
config interface lan
option type bridge
option ifname "eth0"
option proto static
option ipaddr 192.168.1.1
option netmask 255.255.255.0
# WiFi
config interface wifi
option ifname "ath0"
option proto static
option ipaddr 192.168.40.199
option netmask 255.255.255.0
