display only subcategory of a category in product page

[marinela.perju]

Hello,

I have the following problem. For my products I have manufacturer and designer. 
For designer I created a new category Designer and in that I have listed all designers. 

I need now to display in the product page the designer. I managed to show  all the categories for the product. I need help to display only the designer.

 
             <label class="label">Designer:</label>
              {foreach from=Product::getProductCategoriesFull(Tools::getValue('id_product')) item=cat}     
                <li><a href="{$link->getCategoryLink({$cat.id_category})}" title="{$cat.name}">{$cat.name}</a></li>           
              {/foreach}
         

Please help. Maybe there is another solution for this?