Yes you can eat soup that is left out overnight as long as the soup does not contain meat.
if you have left soup out overnight and the soup contains meat then you should throw the soup out because the meat could have bacteria on it that could make you sick.
But if you have no meat in the soup and you just left the soup out overnight then you can safely eat the soup.
Just smell the soup and if it smells good then the soup that was left out overnight is safe to eat but if the soup smells bad then it's not safe to eat.
But you should also boil the soup for around 10 minutes just in case there are any bacteria in the soup as boiling the soup for 10 minutes will kill any bacteria.
So as long as you boil the soup for 10 minutes then it's safe and okay to eat the soup that is left out overnight.
I have eaten soup left out overnight but boiled it first to kill bacteria and it was okay and I never gotten sick.