Schematic symbol for DC barrel jack - and plug?
Normally power connectors have the type of power defined on a schematic. You cannot assume AC or DC without testing or having the schematic. The same applies to what voltage might be there, grounding, etc.

EDIT: There is no plug or socket I know of that is implicitly AC or DC by its shape alone. It must be defined in the schematic or a block diagram if no place else. The builder has the option to silkscreen it on the case next to the socket, which you will see on many wall-warts and desktop power supplies.