file_managed_file_save_upload in modules/file/file.module
Saves any files that have been uploaded into a managed_file element.
locale_translate_import_form_submit in modules/locale/locale.admin.inc
Process the locale import form submission.
system_theme_settings_validate in modules/system/system.admin.inc
Validator for the system_theme_settings() form.
user_validate_picture in modules/user/user.module
Validates an image uploaded by a user.
_file_test_form_submit in modules/simpletest/tests/file_test.module
Process the upload.