Writing a Linux MUSB glue layer should be a more accessible task, as this documentation tries to show the ins and outs of this exercise.
The JZ4740 USB device controller being fairly simple, I hope its glue layer serves as a good example for the curious mind. Used with the current MUSB glue layers, this documentation should provide enough guidance to get started; should anything gets out of hand, the linux-usb mailing list archive is another helpful resource to browse through.