I'm not sure what you mean about uppercase to mean common internet symbols.
I have only heard 'uppercase' used to mean 'capital letters'. The term uppercase originally came from typewriters when the capitals were in a different place on the typewriter, above the small letters (hence uppercase and lowercase).
However nowadays uppercase and capital letters are completely interchangeable as terms.
Upper case (or capital letters): A B C D E F G H I J K L M N O P Q R S T U V X Y Z
Lower case (or small letters): a b c d e f g h i j k l m n o p q r s t u v w x y z