Replace image attributes for lazyload plugin on image elements with specific class

I'm using WordPress and I want to apply lazy load to only certain images. I found here a way to create the data-src attributes and replace the src attribute with the correct image https://wordpress.stackexchange.com/questions/60792/replace-image-attributes-for-lazyload-plugin-data-src. Right now my code applies the lazy load to all the images, and I just want to apply it to the images with the class lazy-load.

This is how my code looks

// Lazyload Converter
function add_lazyload($content) {

$content = mb_convert_encoding($content, 'HTML-ENTITIES', "UTF-8");
$dom = new DOMDocument();
@$dom->loadHTML($content);

$images = [];

foreach ($dom->getElementsByTagName('img') as $node) {
    $images[] = $node;
}

foreach ($images as $node) {
    $fallback = $node->cloneNode(true);

    $oldsrc = $node->getAttribute('src');
    $node->setAttribute('data-src', $oldsrc );
    $newsrc = get_template_directory_uri() . '/assets/placeholders/squares.svg';
    $node->setAttribute('src', $newsrc);

    $oldsrcset = $node->getAttribute('srcset');
    $node->setAttribute('data-srcset', $oldsrcset );
    $newsrcset = '';
    $node->setAttribute('srcset', $newsrcset);

    $noscript = $dom->createElement('noscript', '');
    $node->parentNode->insertBefore($noscript, $node);
    $noscript->appendChild($fallback);
}

$newHtml = preg_replace('/^<!DOCTYPE.+?>/', '', str_replace( array('<html>', '</html>', '<body>', '</body>'), array('', '', '', ''), $dom->saveHTML()));
return $newHtml;
}
add_filter('the_content', 'add_lazyload');
add_filter('post_thumbnail_html', 'add_lazyload');

how can I get the element by class instead of using tag?