Split `missing_docs_in_private_items` into various lints

Would it be feasible and acceptable to split missing_docs_in_private_items into a few different lints? I find myself quite frequently adding #[allow] to enum variants and struct fields, in large part because the naming is typically self-explanatory. Even splitting the lint in two (fields/variants and everything else) would be incredibly useful for me, and would avoid cluttering declarations with unnecessary (imo) #[allow] attributes.

Having different lints for modules and top-level crate documentation would also be great, but are less important to me.