Build armv6 kernel , kernel config file is BEAGLEBONE-CAM
Boot the BBB with the SDHC card inserted
You should see FREAKING LOTS OF DEBUG OUTPUT -- sorry for that :-) After boot you should be able to access two MMC/SD cards on the system, one is built-in eMMC and another one is inserted SD.
Try playing around: diskinfo -v sdda{0,1}, geom disk list, camcontrol devlist.
Unfortunately camcontrol devlist doesn't display useful data about the cards right now, this requires modifying camcontrol userspace utility, this is WIP.