Proper enqueue for child theme functions.php

I was just setting up a parent theme recently and needed to create a snippet for other theme authors to use. These two in combination will load the correct style.css files, and in the correct order (child being loaded after parent).

In your parent theme’s functions.php file:

function wpse_175802_scripts() {
    // Load our main stylesheet.
    wp_enqueue_style( 'wpse-175802-style', get_stylesheet_uri() );
}
add_action( 'wp_enqueue_scripts', 'wpse_175802_scripts' );

In your child theme’s functions.php file:

function wpse_175802_child_theme_scripts() {
    wp_enqueue_style( 'parent-theme-css', get_template_directory_uri() . '/style.css' );
}
add_action( 'wp_enqueue_scripts', 'wpse_175802_child_theme_scripts' );

If you wanted the custom.css files loaded, keep them in the child_theme_scripts function, following the same format as you used for the parent’s style.css file.

Credit to the Codex and http://kovshenin.com/2014/child-themes-import/ for the original snippets.