Display all subterms of a custom taxonomy filtered by parent terms

I have a custom taxonomy which i called ‘fonte’ that should display a list of books. These are divided in two parent terms, ‘mixed’ or ‘single’. So the hierarchy is something like that:

Mixed

• book1
• book2
• book3 …

Single

• book4
• book5
• book6

I’d like the page template to show the two parent terms ‘mixed’ and ‘single’ as selectable filters, so that when I click on one of them they display their child terms, but I believe I’m not able to do this.

What I have so far:

          <?php
      $terms = get_terms( 'fonte' );

      ;

      foreach ( $terms as $term ) {
      if ($term->parent != 0){
      // The $term is an object, so we don't need to specify the $taxonomy.
      $term_link = get_term_link( $term );

      // If there was an error, continue to the next term.
      if ( is_wp_error( $term_link ) ) {
          continue;
      }

      // We successfully got a link. Print it out.
      echo '  <div class="element">


          <div class="pf-body c27-content-wrapper"><a href="' . esc_url( $term_link ) . '">' . $term->name . '</a>        </div>
                </div>';
      echo  $term->description; // This will return the description of the term

      }

}
;
?>