Using the EE PSR-4 autoloader

pi.my_addon.php

<?php

$plugin_info = array(
    'pi_name'   => 'My Addon',
    'pi_version'  => '1.0.0',
    'pi_author'   => 'Rob Sanchez',
    'pi_author_url' => 'https://github.com/rsanchez',
    'pi_description'=> '',
    'pi_usage'    => ''
);

class My_addon
{
    public function __construct()
    {
        global $AUTO;

        $AUTO->addPrefix('MyAddon', PATH_THIRD.'my_addon/src/MyAddon/');
    }
}