How to get rid of Git submodules untracked status?

I can't seem to get rid of untracked content in Git's submodules. Running git status yields:

# On branch master
# Changes not staged for commit:
#   (use "git add ..." to update what will be committed)
#   (use "git checkout -- ..." to discard changes in working directory)
#   (commit or discard the untracked or modified content in submodules)
#
#    modified:   bundle/snipmate (untracked content)
#    modified:   bundle/surround (untracked content)
#    modified:   bundle/trailing-whitespace (untracked content)
#    modified:   bundle/zencoding (untracked content)
#
no changes added to commit (use "git add" and/or "git commit -a")

Adding the --ignore-submodules parameter hides these messages; but I wonder if there's a way to get rid of this dirt in a more suitable, core-ish, manner.

Solution

Since the git status reports untracked content, the actual way to have a clean status would be to go into each one of those submodules and:

add and commit the untracked contents,
or reference the untracked contents in a .gitignore specific to each module.
or you can add the same ignored content to the submodule's .git/info/exclude, as peci1 reports in the comments.
or add dirty to the submodule specification, as mentioned in ezraspectre's answer (upvoted).
```
git config -f .gitmodules submodule.<path>.ignore untracked
```
or add a global .gitignore file (often ~/.gitignore-global). Like for example .DS_Store or in my case Carthage/Build as reported by Marián Černý in the comments. See .gitginore man page:

Patterns which a user wants Git to ignore in all situations (e.g., backup or temporary files generated by the user’s editor of choice) generally go into a file specified by core.excludesFile in the user’s ~/.gitconfig. Its default value is $XDG_CONFIG_HOME/git/ignore. If $XDG_CONFIG_HOME is either not set or empty, $HOME/.config/git/ignore is used instead.