Artesyn ATCA-8310 Installation and Use (May 2014) - Manual (Page 181)

U-Boot
ATCA-8310 Installation and Use (6806800M72E) 181
A device identifier is actually a combination of interface, device and partition, separated by
colons. For example "usb:0:0" for the 1st partition on the 1st USB storage device.
If the interface is "usb", it may contain a numerical suffix defining the USB controller (e.g. usb0
or usb1). The USB controller is reset ("usb reset" command) before looking for
devices/partions/files on it).
Device and partition numbers may be:
 Numerical values
 Range values in the form "[<start>-<end>]"
 A wildcard "*" for all existing devices or partitions
Non-existing devices/partitions are silently skipped.