Sazaj

This works for me:

// Customize Logo instead of Text
function themeslug_theme_customizer( $wp_customize ) {
    $wp_customize->add_section( 'themeslug_logo_section' , array(
        'title'       => __( 'Logo', 'themeslug' ),
        'priority'    => 30,
        'description' => 'Upload a logo to replace the default site name and description in the header',
    ) );

    $wp_customize->add_setting( 'themeslug_logo',
        'sanitize_callback' == 'esc_url_raw'
    );

    $wp_customize->add_control('themeslug_logo',
        array( 'default' => '',
            'sanitize_callback' => 'esc_url_raw',
            'type' => 'theme_mod',
        ));

    $wp_customize->add_control( new WP_Customize_Image_Control( $wp_customize, 'themeslug_logo', array(
        'label'    => __( 'Logo', 'themeslug' ),
        'section'  => 'themeslug_logo_section',
        'settings' => 'themeslug_logo',
        'sanitize_callback' => 'esc_url_raw',
    ) ) );
}
add_action( 'customize_register', 'themeslug_theme_customizer' );