I'm not sure then how you want to get any device information, when device doesn't work with SNMP and WMI protocols.
For such case, I think that you can try to use "Data Connector" functionality to import pre-defined .xml or .csv file in "Symantec_CMDB", where you will specify all required information about these devices (Their MAC, IP, Name, etc).
Basic example of .csv columns for further import:
Name Domain User OS Name OS Version IP Address MAC Address System Type OS Revision