Dilution is the only solution.
I make soup with unseasoned homemade stock and (mostly) only season at the end. If I'm sauteeing aromatics or something, I can season along the way without running the risk of making the broth too salty. Seasoning at the end is the easiest way to ensure that you have the salt/acid balance right. If you season too early, or if you use off-the-shelf chicken stock, the soup will lose volume as it sits there and get saltier and saltier. Another advantage of using stock rather than broth is that you can reduce it down if you want to amp up the flavor (without amping up the sodium content). I add herbacious notes about 25 minute out before I want to serve, remove them, season with salt/fish-sauce/soy-sauce and add some brightness in with sherry vinegar or lemon juice.