Probhat is currently most popular keyboard layout for writing Bengali in
linux. Please add it in by default.

These are the codes I added to my configuration file to define my own
Probhat layout:

;; Probhat Input Method

(quail-define-package
 "probhat" "Bengali-probhat" "probhat" t
 "Porbhat for Bangla" nil t nil nil nil nil nil nil nil nil t)

(quail-define-rules
  ("!" ?!)
  ("1" ?১)
  ("@" ?@)
  ("2" ?২)
  ("#" ?#)
  ("3" ?৩)
  ("$" ?৳)
  ("4" ?৪)
  ("%" ?%)
  ("5" ?৫)
  ("^" ?^)
  ("6" ?৬)
  ("&" ?ঞ)
  ("7" ?৭)
  ("*" "ৎ")
  ("8" ?৮)
  ("(" ?()
  ("9" ?৯)
  (")" ?))
  ("0" ?০)
  ("_" ?_)
  ("-" ?-)
  ("+" ?+)
  ("=" ?=)
  ("Q" ?ধ)
  ("q" ?দ)
  ("W" ?ঊ)
  ("w" ?ূ)
  ("E" ?ঈ)
  ("e" ?ী)
  ("R" ?ড়)
  ("r" ?র)
  ("T" ?ঠ)
  ("t" ?ট)
  ("Y" ?ঐ)
  ("y" ?এ)
  ("U" ?উ)
  ("u" ?ু)
  ("I" ?ই)
  ("i" ?ি)
  ("O" ?ঔ)
  ("o" ?ও)
  ("P" ?ফ)
  ("p" ?প)
  ("{" ?ৈ)
  ("[" ?ে)
  ("}" ?ৌ)
  ("]" ?ো)
  ("A" ?অ)
  ("a" ?া)
  ("S" ?ষ)
  ("s" ?স)
  ("D" ?ঢ)
  ("d" ?ড)
  ("F" ?থ)
  ("f" ?ত)
  ("G" ?ঘ)
  ("g" ?গ)
  ("H" ?ঃ)
  ("h" ?হ)
  ("J" ?ঝ)
  ("j" ?জ)
  ("K" ?খ)
  ("k" ?ক)
  ("L" ?ং)
  ("l" ?ল)
  (":" ?:)
  (";" ?;)
  (""" ?")
  ("'" ?')
  ("|" ?॥)
  ("" ?‌)
  ("~" ?~)
  ("`" ?‍)
  ("Z" ?য)
  ("z" ?য়)
  ("X" ?ঢ়)
  ("x" ?শ)
  ("C" ?ছ)
  ("c" ?চ)
  ("V" ?ঋ)
  ("v" ?আ)
  ("B" ?ভ)
  ("b" ?ব)
  ("N" ?ণ)
  ("n" ?ন)
  ("M" ?ঙ)
  ("m" ?ম)
  ("<" ?ৃ)
  ("," ?,)
  (">" ?ঁ)
  ("." ?।)
  ("?" ??)
  ("/" ?্))