How to prevent a kernel module from opening a specific device? I am using two devices, one of which requires usbserial for proper operation (a GPS, using gpsd; this guide specifies that usbserial is required), and one of which requires usbserial to be unloaded (the FTDI FT232H; this guide specifies that `rmmod usbserial` must be run to use the D2XX drivers). Is there some way that I can instead add rules to prevent usbserial from touching the FTDI device, while still allowing gpsd to use usbserial?

You can use the _unbind_ interface in sysfs. Please refer to this article for details. You will find instructions for automating the unbind upon discovery of the device in this answer.