[ISDB_LDT_linkage_descriptor.description_type]
Bits = 4
0x0 = Undefined
0x1 = Described with short_event_descriptor
0x2 = Described with extended_event_descriptor (Independent type without describing item_description)
0x3 = Described with extended_event_descriptor
0x4-0xE = Reserved
0x0F = Others (Including not specified descriptor and mixed)
