Add custom customizer sections / panels for Wordpress child theme

custom-child-theme-customizer.php

<?php

function fod_custom_customizer_options( $wp_customize ) {

    $wp_customize->add_section( 'fod_options' , array(
    'title'      => __('Homepage Popup Form'), 
    'panel'      => '',
    'priority'   => 1000
    ) ); 

    $wp_customize->add_setting(
        'fod_home_popup_form',
        array(
            'default'         => '',
            'transport'       => 'refresh'
        )
    );
    $wp_customize->add_control(
          new WP_Customize_Control(
              $wp_customize,
              'fod_home_popup_form_code',
              array(
                  'label'          => __( 'Homepage Popup Form', 'respondocustomizer' ),
                  'description' => __( 'Edit the popup form here.', 'respondocustomizer' ),
                  'section'        => 'fod_options',
                  'settings'       => 'fod_home_popup_form',
                  'type'           => 'textarea'
              )
          )
     );
}
add_action( 'customize_register', 'fod_custom_customizer_options' );