MAJ:MIN in Linux

Each device file has a major ID number and a minor ID number. The major ID identifies the general class of device, and is used by the kernel to look up the appropriate driver for this type of device. The minor ID uniquely identifies a particular device within a general class. The major and minor IDs of a device file are displayed by the ls ­-l command.
Each device driver registers its association with a specific major device ID, and this association provides the connection between the device special file and the device. The name of the device file has no relevance when the kernel looks for the device driver.