Serial console? That’s beautiful when it comes to debugging. The following images are specific to the Seagate GoFlex Home, however, you may be able to figure out the connections for other Marvell SoCs.
On the GoFlex Home:
10 9 8 7 6 5 4 3 2 1 1 => GND (Ground for the serial communication) 2 => RX (Receiving bits) 3 => TX (Transmitting bits)
Note: The RX and TX are interchanged at one end, this is because the RX of the GoFlex becomes the TX of the USB adapter, and vice cersa.
After you connect the USB end to your desktop/laptop, you can use screen to display the serial console:
# screen /dev/ttyUSB0 115200
The serial console is especially useful for debugging the kernel boot and setting the u-boot environment.