some more inter-doc links to make RCC usage easier

Author: TheZoq2

src/gpio.rs

@@ -2,13 +2,16 @@
 //!
 //! The GPIO pins are organised into groups of 16 pins which can be accessed through the
 //! `gpioa`, `gpiob`... modules. To get access to the pins, you first need to convert them into a
-//! HAL designed struct from the `pac` struct using the `spilit` function.
+//! HAL designed struct from the `pac` struct using the [split](trait.GpioExt.html#tymethod.split) function.
 //! ```rust
 //! // Acquire the GPIOC peripheral
 //! // NOTE: `dp` is the device peripherals from the `PAC` crate
 //! let mut gpioa = dp.GPIOA.split(&mut rcc.apb2);
 //! ```
 //!
+//! See the documentation for [rcc::APB2](../rcc/struct.APB2.html) for details about the input parameter to
+//! `split`.
+//!
 //! This gives you a struct containing two control registers `crl` and `crh`, and all the pins
 //! `px0..px15`. These structs are what you use to interract with the pins to change their modes,
 //! or their inputs or outputs. For example, to set `pa5` high, you would call

src/rcc.rs

@@ -36,6 +36,14 @@ impl RccExt for RCC {
 }
 
 /// Constrained RCC peripheral
+///
+/// Aquired by calling the [constrain](../trait.RccExt.html#tymethod.constrain) method
+/// on the Rcc struct from the `PAC`
+///
+/// ```rust
+/// let dp = pac::Peripherals::take().unwrap();
+/// let mut rcc = dp.RCC.constrain();
+/// ```
 pub struct Rcc {
     /// AMBA High-performance Bus (AHB) registers
     pub ahb: AHB,