A soup can be defined as a food dish that contains both broth and pieces of meat It should also contain other ingredients such as vegetables and dumplings. Chicken and dumplings possess all of these so it's a soup.
Sooooo....is stew a soup as well? How about chili? Perhaps a couple better questions are: What is soup? What is stew?
1) a liquid dish, typically made by boiling meat, fish, or vegetables, etc., in stock or water. "a bowl of tomato soup"
2) a substance or mixture perceived to resemble soup in appearance or consistency. "the waves and the water beyond have become a thick brown soup"
1) a dish of meat and vegetables cooked slowly in liquid in a closed dish or pan. "lamb stew"
2) a state of great anxiety or agitation. "I suppose he's all in a stew"
Therefore, both soup and stew are "liquid broths" with meats and vegetables. I guess the only real difference between the two is the volume of broth to other ingredients is the time spent cooking (boiling vs. cooked slowly), and if the lid is on or off....
When properly prepared, chicken and dumplings is thick like a cream sauce, not watery like a bowl of tomato soup. If the broth is thin, then its chicken soup with bread floating around in it...and wrong!