I don't know the exact source but all food items of the same category can be consumed after reciting a single bracha.
For example, if you have in mind to eat/drink tea, fish and ice cream you can say a single shehakol to cover all the items.
Is there a precise definition with all the criteria for "having in mind"?
If you usually have tea following a meal, but you don't have it in mind at the time of a bracha do you repeat the shehakol?
How about if you said a bracha in one room (living room) and began eating a separate item in a separate room (bed room) of the same house? Do you need to have in mind all the places you are going to eat?