I just added it to your plugin general.php file and it works:
Line 193 Function:
function mtphr_post_block( $atts, $content = null ) {
extract( shortcode_atts( array(
'id' => '',
'class' => '',
'type' => 'post',
'orderby' => 'date',
'order' => 'DESC',
'offset' => '0',
'trim' => 120,
'category_name' => 'news'
), $atts ) );
Would like it to work as a parameter though..