I think that in conjunction with his previous wording in the hikey forum, we may be able to assume that he meant “coms” as reference to that old term “com port”, which is RS-232, whereas the UART on these boards operate at logic level, so the answer would be that without conversion circuitry (such as a MAX232), there are no ports meeting the specifications he is looking for. Also, its not entirely correct that there is only one dragonboard. True that there is only one 96boards dragonboard, but there are dragonboards from before 96boards. Intrinsyc made a dragonboard 800 and 810.
edha: In theory, you could add a large number of RS-232 ports to the board through the use of USB-to-RS232 adapters, such as those utilizing ftdi or pl2303. Just make sure that they match up with the devices you are trying to connect with, since these devices are available in TTL, RS-232, and RS-422 version. Maybe one of these FTDI modules;
http://www.ftdichip.com/Products/Modules/USBRSxxx.htm look at the USB-COM232-PLUS4 module, it takes a single USB and splits off FOUR RS-232 ports.
But be aware that the Dragonboard 410c only actually has ONE USB2.0 port. The others are provided through a switch and a hub, so don’t go too crazy with adding on tons of USB devices.