i need to define a custom support feature for my Wordpress Plugin but i can't find how to do so.

What i want to do is to display a box on certain custom post type containing 2 meta fields in which users can type in Longitude and Latitudes values for geolocalisation purposes.

For practical uses, i want to attach this custom feature the same way as supports are to posts : 

    <?php
    $args = array(
        ...
        ...
        'supports' => array('title','editor', 'thumbnail', 'my_custom_support'),
        ...
        ...
    );
    register_post_type('my_custom_post_type', $args);
    ?>

OR, if my custom post type has already been created beforehand: 

    <?php
    add_post_type_support('my_custom_post_type', 'my_custom_support');
    ?>

I know what i want but i just can't find how to register new supports ...

I hope someone can answer this problem because i'm actually tearing off my hairs !