The device files in the /devices directory are also called the device tree.
The device tree shows relationships among devices. In the device tree, a directory represents a nexus device. A nexus is a device that can be a parent of other devices. In the following example, pci@1f,0 is a nexus device. Only selected output from the command is shown.
# ls -l /devices drwxr-xr-x 4 root sys 512 date time pci@1f,0/ crw------- 1 root sys 111,255 date time pci@1f,0:devctl
You can use prtconf(1M) or prtpicl(1M) to see a graphic representation of the device tree. See Overview of the Device Tree in Writing Device Drivers for more information about the device tree.