Place to add the code

I have a short question.

What is the best way to put php code in your theme (in this case, I mean woocommerce hooks).

I have a child theme. Is it best to add them in the functions.php file or extract specific files from the main theme and load them into the child theme and add the code there?

Code example:

add_action(‘woocommerce_after_shop_loop_item’, ‘function_name’,5 );

function function_name(){
echo do_shortcode(“[shortcode name]”);
}