Soybean paste is a broad category of savory pastes made with soybeans, often fermented with salt and sometimes grains. It includes products with different ingredients, fermentation methods, salt levels and textures.
Korean doenjang and Japanese miso are distinct examples, not interchangeable names for every soybean paste. Check the product specified by a recipe before substituting, particularly where seasoning strength, sweetness or grain content matters.
Reference: Further reading.