bb-mode is a major mode for editing bitbake recipe files in Emacs. It does basic syntax highlighting and handles comments (M-;).
(require 'bb-mode)
(setq auto-mode-alist (cons '("\\.bb$" . bb-mode) auto-mode-alist))
(setq auto-mode-alist (cons '("\\.inc$" . bb-mode) auto-mode-alist))
(setq auto-mode-alist (cons '("\\.bbappend$" . bb-mode) auto-mode-alist))
(setq auto-mode-alist (cons '("\\.bbclass$" . bb-mode) auto-mode-alist))
(setq auto-mode-alist (cons '("\\.conf$" . bb-mode) auto-mode-alist))