Although overriding the function in a child theme is often a good way to go, it looks like this theme doesn’t set that up with this particular function (because they’re not checking if function_exists() first, before redefining it – which will cause an error).
However, they have given you a way of overriding it with filters.
At the bottom of their function, everything they return is being run through the cherry_get_site_logo filter.
Everytime you see apply_filters() being run in someone else’s code, this is something you can hook into 🙂
To hook into this, you need to add your own filter function. In your function, you can either change their output (eg. through something like str_replace() or preg_replace() to replace parts of it), or you can simply ignore what they’ve done and provide your own output (which I understand is what you’re after).
So in this case, to override the output of their function, you just need to:
add_filter("cherry_get_site_logo", "wpse_226159_site_logo");
function wpse_226159_site_logo($logo, $location){
$logo = "This is my overriden logo";
return $logo;
}
This will completely replace their logo output with the text This is my overriden logo. Obviously replace that with whatever you like.
This code goes in your child theme’s functions.php file.