Shortcode for Home Page collection of reviews?

Hi, I have the widget in place on the homepage and text box ready. However, I have question with the shortcode to display a collection of total of 20 reviews from across the site e.g. any reviews + any category… It is for home page testimonial section, in masonry layout…Please advise the shortcode for: 20 reviews – sitewide any product(s) – any category. (Hopefully a mix of reviews from the site).

Thanks