Upload custom post type files in another folder.

functions.php

<?php
/**
 * Upload custom post type files in another folder
 * @author Mostafa soufi <mostafa.soufi@hotmail.com>
 */
add_filter( 'upload_dir', function($args) {
	if( !isset($_REQUEST['post_id']) ) {
		return $args;
	}

	$post_type_name = get_post_type( $_REQUEST['post_id'] );

	if( $post_type_name = 'custom_post_type' ) {
		// Set the new path depends on current post_type
		$newdir = '/' . $post_type_name;
		$args['path']    = str_replace( $args['subdir'], '', $args['path'] ); //remove default subdir
		$args['url']     = str_replace( $args['subdir'], '', $args['url'] );
		$args['subdir']  = $newdir;
		$args['path']   .= $newdir;
		$args['url']    .= $newdir;
		return $args;
	}

	return $args;
} );