more specific ref to link_section attributes

Author: tstellanova

cortex-m-rt/src/lib.rs

@@ -392,9 +392,11 @@
 //! Some microcontrollers provide additional memory regions beyond RAM and FLASH.
 //! For example, some STM32 devices provide "CCM" or core-coupled RAM that is
 //! only accessible from the core. In order to access these using
-//! `#[link_section=".foo"]` from your code, you need to modify `memory.x`
+//! [`link_section`] attributes from your code, you need to modify `memory.x`
 //! to declare the additional sections:
 //!
+//! [`link_section`]: https://doc.rust-lang.org/reference/abi.html#the-link_section-attribute
+//!
 //! ```text
 //! MEMORY
 //! {