Add custom prefix to name image when upload

Past code to function.php in Child theme

Change xsolution- to your prefix

// them ten thuong hieu cho hinh anh tai len

add_filter('wp_handle_upload_prefilter', 'custom_upload_filter' );
function custom_upload_filter( $file ){
$file['name'] = 'xsolution-' . $file['name'];
return $file;
}