OpenIPC has support for motors on many devices through a variety of means. Many of these can be found in the motors repo.
Some motors can be controlled through a binary or kernel module. ingenic-motor is an example of this. Hex messages are sent to the module that in turn move the motor. xm-kmotor does this as well. View their READMEs for more information on configuration.
Some motors can be controlled through a UART TTY device. See xm-uart.
This is a simple and direct method to control a stepper motor by setting off GPIOs to a component on the board that assists in driving the motor. As long as you can probe your board and determine which GPIOs are connected to something like a ULN2803, there's a good chance you'll be able to control it.
With onvif_simple_server you can easily gain access to PTZ controls through ONVIF. Functionality will vary depending on the motor control package you use. See the server's example config in it's repo for all of the available commands.