In the case of drivers, a lot depends on the specific hardware. Some drivers are written by employees of the hardware manufacturer, some are written by employee

In the case of drivers, a lot depends on the specific hardware. Some drivers are written by employees of the hardware manufacturer, some are written by employees of companies using FreeBSD, and some are written by interested volunteers. Hardware vendors have an interest in supporting whichever FreeBSD versions are of interest to their customers, and often merge to all supported branches.