Serial and parallel ports are certainly desirable—and highly recommended—but not required. The 16550 component with 16-byte FIFOs is suitable for QNX Neutrino. Our drivers can work with these devices on a byte-aligned or doubleword-aligned manner.
If you're going to support multiple serial ports on your device, you can have the multiple devices share the same interrupt. It's up to the software to decide which device generated the interrupt and then to handle that interrupt. The standard QNX Neutrino serial port handlers are able to do this.
Although the serial driver can be told to use a "nonstandard" clock rate when calculating its divisor values, this can cause the baud rate to deviate from the standard.
Try to run DTR, DSR, RTS, CTS if possible, because hardware flow control will help on slower CPUs.