downloading firmware other than UART1

Does anybody know how to download an openAT app/firmware through UART2 or USB (not DOTA or UART1)?
at the moment we are using at+wdwl and xmodem from hyperterm, or TMT “download Open AT” menu command, but it only works on UART1
Q2686 + Q26 development board

See: viewtopic.php?f=36&t=2303