Override html.tpl.php per node type
The name of a preprocess function is based on the theme/template that is being processed. To preprocess the html.tpl.php file you'll need to use hook_preprocess_html():

function media_preprocess_html(&amp;$vars) {
  $node = menu_get_object();

  if ($node &amp;&amp; $node-&gt;nid) {
    $vars['theme_hook_suggestions'][] = 'html__' . $node-&gt;type;
  }
}