How to add Site Logo support to a theme

add-theme-support-for-custom-logo.php

<?php
/*
 * First we need to let WordPress know that our theme supports the output of the "custom-logo"
 * We do this by making the "add_theme_support( 'custom-logo' ) plus arrays declaration as follow.
 * File: functions.php
 */
function themename_setup() {
    add_theme_support( 'custom-logo', array(
		'height'      => 250,
		'width'       => 75,
		'flex-height' => true,
	) );
}
add_action( 'after_setup_theme', 'themename_setup' );

/*
 * We then need to create a function that will return our uploaded logo in the header template or whereever we choose to add the logo.
 * File: functions.php
 */

if ( ! function_exists( 'themename_the_custom_logo' ) ) {
/**
 * Displays the optional site logo.
 *
 * Returns early if the site logo is not available.
 *
 * @since ThemeName 1.0.0
 */
    function themename_the_custom_logo() {
	    if ( function_exists( 'the_custom_logo' ) ) {
		    the_custom_logo();
	    }
    } // We can now call this function in place where we want the logo to appear
}

/*
 * Note that you will need to add some CSS to adjust the logo position that best suites your theme.
 */