The stock firmware has a recovery mode triggered by holding down the reset button on power-up or hitting escape at the serial console. The recovery interface is accessible via HTTP at 192.168.1.10. The OpenWrt factory image is compatible.
When connected to the serial console, it is possible to drop into a u-boot prompt by hitting 'q' in recovery mode. Note that there is no saved u-boot environment on flash, so you will have to set e.g. serverip every time you need to use TFTP.
The SoC's builtin Ethernet is connected to a IP175C 5-port 100mbit switch. VLAN setup is supported in OpenWRT.
The serial port is located at JP2 on the board. The baud rate is 57600.