function field_name_upload_prefilter($errors) {
//Add a WP filter that alters the upload path
add_filter('upload_dir', 'field_name_upload_dir');
return $errors;
}
function field_name_upload_dir($uploads) {
//Change the path
$uploads['path'] = $uploads['basedir'].'/tsf-xxx';
$uploads['url'] = $uploads['baseurl'].'/tsf-xxx';
$uploads['subdir'] = '';
return $uploads;
}
add_filter('acf/upload_prefilter/name=tsf_file_upload', 'field_name_upload_prefilter');
tsf_file_upload = The ACF name
/tsf-xxx = Name of the directory in the uploads folder