You can bring frozen soup on a plane either in your checked baggage or through your carry on luggage.
But the frozen soup or liquid must be completely frozen when it goes through the security checkpoint and if the frozen soup has thawed it will not be allowed through the security.
So make sure to keep the soup completely frozen and you can keep the soup frozen in your carry on or checked baggage using dry ice.
The dry ice will not melt like regular ice would and will be allowed through the airport security.
Anything liquids or soups can be brought onto the plane as long as it's completely frozen and not melted at all.