This implements a safe and relatively simple API over the netlink API,
that allows you to add different attributes to a netlink message and
broadcast it. As the first user of this API only makes use of broadcast,
only broadcast messages are supported here.

This API is intended to be safe and to be easy to use in *generated*
code. This is because netlink is generally used with yaml files that
describe the underlying API, and the python generator outputs C code
(or, soon, Rust code) that lets you use the API more easily. So for
example, if there is a string field, the code generator will output a
method that internall calls `put_string()` with the right attr type.

Reviewed-by: Matthew Maurer <mmaurer@google.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Carlos Llamas <cmllamas@google.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260707-binder-netlink-v7-2-42b40e4b1ac8@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

To ensure that networking code can be found in a single shared place,
add it to the relevant NETWORKING entry. The net.rs file is moved into
the net/ directory so that it's included under the MAINTAINERS entry
without needing a separate rust/kernel/net.rs entry.

Reviewed-by: Carlos Llamas <cmllamas@google.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260707-binder-netlink-v7-1-42b40e4b1ac8@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>