Adding meta fields to attachments

WP attachment metas

/*
 * Meta fields for media uploads
 */

/*
 * @param array $form_fields
 * @param object $post
 *
 * @return array
 */
function add_attachment_fields_to_edit ( $form_fields, $post )
{

    $form_fields[ "name_for_this_field" ] = array(
        'label' => __ ( "Title for this field", 'domain' ),
        'input' => 'text',
        'value' => get_post_meta ( $post->ID, 'name_for_this_field', TRUE ),
        'helps' => 'Help text, if desired'
    );

    return $form_fields;
}

add_filter ( "attachment_fields_to_edit", "add_attachment_fields_to_edit", NULL, 2 );

/*
 * @param array $post
 * @param array $attachment
 *
 * @return array
 */
function add_attachment_fields_to_save ( $post, $attachment )
{

    if ( isset( $attachment[ 'name_for_this_field' ] ) ) {
        update_post_meta ( $post[ 'ID' ], 'name_for_this_field', $attachment[ 'name_for_this_field' ] );
    }

    return $post;
}

add_filter ( 'attachment_fields_to_save', 'add_attachment_fields_to_save', NULL, 2 );