Hook function for admin/structure/taxonomy/your_vocaburary form (Save and Reset to alphabetical) I'm looking for a hook function to interact with the buttons "Save" and "Reset to alphabetical" on taxonomy term hierarchy. Does anyone know how to override this functionality?
with hook_form_FORM_ID_alter you can add extra function to trigger on submit.here is a simple example for you :

/**
 * Impelement hoo_form_FORM_ID_alter
 * @param array $form
 * @param type $form_state
 * @param type $form_id
 */
function MODULENAME_form_taxonomy_overview_terms_alter(&amp;$form, $form_state, $form_id) {
    $form['#submit'][] = 'my_news_submit';
}

function my_news_submit($form, &amp;$form_state) {
    if ($form_state['triggering_element']['#value'] == t('Reset to alphabetical')) { // check if reset button submited or not
        drupal_set_message('RESET CALLED');
        // ADD YOUR EXTRA WORKS HERE FOR RESET 
    } else { // act on "save" button submited
        drupal_set_message('SAVED CALLED');
       // ADD YOUR EXTRA WORKS HERE FOR SUBMIT
    }
}