Árbol binario de Haskell con solo caracteres

Lets say I make my tree like this

data Tree a = EmptyTree | Node a (Tree a) (Tree a) deriving (Show, Read, Eq)

But I want to make a tree that uses only chars I don't need it to be template. I know my tree will use only chars if I make it like the one above I can't make if dataOfNode == ')' in a function because It says that it is a [char] type and it expects [a] type.

How to make a tree that would use only chars or is there a way to make this type of check dataOfNode == ')' with this type of tree that I gave. Can you give me a short example of a function that let's say check if the data in this node is the sign ')' ?

Edit:
As requested I am posting the function that I would like to make `

buildTreeHelper :: (Ord a) => String -> a -> Int -> String -> Tree a -> Tree a
buildTreeHelper str blank turn path t
 | str == [] = t
 | front == '(' = buildTreeHelper (tail str) blank 1 ('L':path) (expandTree (reverse path) blank t)
 | front == ')' = buildTreeHelper (tail str) blank 2 (tail path) t
 | turn == 1 = buildTreeHelper (tail str) blank 2 (tail path) (expandTree (reverse path) front t)
 | turn == 2 = buildTreeHelper (tail str) blank 3 ('R':path) (expandTree (reverse path) front t)
 | turn == 3 = buildTreeHelper (tail str) blank 2 (tail path) (expandTree (reverse path) front t)
 where 
  front = head str

Logically it is not finished but also I can't use it because it takes a string which I divade char by char. That's why I am sure I want to make my Tree only from chars so I can replace type a a type char at the begining of the function. It has other mistakes too but I think the main idea is clear.