Barkley was a surprise inclusion in Roy Hodgson's squad for the forthcoming World Cup qualifiers against Moldova and Ukraine.
"It is really good," said Martinez. "It is terrific reward. He has always shown special potential. He is well known within the FA. Ross is first to know he is within middle of developing period.
"It's great he has had that call, it's a sign that England manager is keeping an eye on him. But it doesn't change his role within the Under-21s. He is not a player who needs to be reminded on a daily basis (to keep his feet on the floor). He knows what he needs to do to progress."
For the big stories and the banter follow us on Twitter: @tribalfootball