/usr/mipsisa32r6-linux-gnu/include/linux/usb/ is in linux-libc-dev-mipsr6-cross 4.15.0-18.19cross1.
This file is owned by root:root, with mode 0o755.
..
/usr/mipsisa32r6-linux-gnu/include/linux/usb/audio.h
/usr/mipsisa32r6-linux-gnu/include/linux/usb/cdc-wdm.h
/usr/mipsisa32r6-linux-gnu/include/linux/usb/cdc.h
/usr/mipsisa32r6-linux-gnu/include/linux/usb/ch11.h
/usr/mipsisa32r6-linux-gnu/include/linux/usb/ch9.h
/usr/mipsisa32r6-linux-gnu/include/linux/usb/charger.h
/usr/mipsisa32r6-linux-gnu/include/linux/usb/functionfs.h
/usr/mipsisa32r6-linux-gnu/include/linux/usb/g_printer.h
/usr/mipsisa32r6-linux-gnu/include/linux/usb/gadgetfs.h
/usr/mipsisa32r6-linux-gnu/include/linux/usb/midi.h
/usr/mipsisa32r6-linux-gnu/include/linux/usb/tmc.h
/usr/mipsisa32r6-linux-gnu/include/linux/usb/video.h