function prefixeplugin_upgrade($nom_meta_base_version, $version_cible) {
	$maj = array();
	$maj['create'] = array(
		array('maj_tables',array('table1','table2')),
		array('maj_config', array('prefixeplugin')),
	);

	$maj['0.2.0'] = array(
		array('sql_alter',"bla bla..."),
		array('maj_config_020'),
	);

	$maj['0.3.0'] = array(
		array('sql_alter',"bla bla..."),
		array('ecrire_config','prefixeplugin/variable', 'defaut'),
	);

	include_spip('base/upgrade');
	maj_plugin($nom_meta_base_version, $version_cible, $maj);
}

 function maj_config_020() {
 	// code de l'upgrade...
 }