The device tree include file for TI TPS65* is in a relative path to the source for example:
https://cgit.freebsd.org/src/tree/sys/contrib/device-tree/src/arm/ti/omap/am335x-bone-common.dtsi#n305
https://cgit.freebsd.org/src/tree/sys/contrib/device-tree/src/arm/rockchip/rk3066a-marsboard.dts#n183
That will produce an error like:
root@beaglebone:/usr/src/sys/modules/dtb/am335x # make
Warning: Object directory not changed from original /usr/src/sys/modules/dtb/am335x
/usr/src/sys/tools/fdt/make_dtb.sh /usr/src/sys /usr/src/sys/contrib/device-tree/src/arm/ti/omap/am335x-bone.dts /usr/src/sys/modules/dtb/am335x
Error at <standard input>:3645:11: Unable to locate input file
/include/ "../../tps65217.dtsi"
This patch gets the dts path and adds that as an include path for the device tree compiler.