Override Shortcode in WordPress Child Theme

add_action('init', 'remove_parent_theme_shortcodes');
function remove_parent_theme_shortcodes() {
  // remove shortcode from parent theme
  // shortcode_name should be the name of the shortcode you want to modify
  remove_shortcode( 'shortcode_name' );

  // add the same shortcode in child theme with our own function
  // note to self: think of a better example function name
  add_shortcode( 'shortcode_name', 'hdev_child_theme_shortcode_name' );
}

function hdev_child_theme_shortcode_name( $atts ) {
  // write your shortcode function here.
}