Adding a usb keyboard driver to a custom Linux firmware

I have a router running a custom Linux as firmware. I can ssh in and install packages via the entware repository. I’ve attached a keyboard to the USB port and I’d like to read the keyboard input. The keyboard appears in lsusb but /dev/input does not exist. I’m assuming the input drivers were removed as part of the customization. Can I add a generic Linux keyboard driver to my firmware? Can I just go to an existing Linux machine and copy the keyboard driver from /dev/input? If not, what else could I try?