Why can't I override my menu in Drupal 7 with theme_menu_tree?
Drupal 7 theme can implement a THEMENAME_menu_tree__MENU_NAME() or THEMENAME_menu_link__MENU_NAME() function to override theme_menu_tree() or theme_menu_link() for a specific menu.


References for overriding the specific menu:


https://gist.github.com/gagarine/3201854
https://gist.github.com/henrijs/6225177


Can you once try passing $variables as reference to the THEMENAME_menu_tree__MENU_NAME() as below:

function storm_menu_tree__menu_social_media($variables) {
  return '&lt;span class="test-menu"&gt;' . $variables['tree'] . '&lt;/span&gt;';
}


Note: Clear the cache after making the changes to the code in order to make sure implemented changes reflects on the site.