Better document finding ioctl documentation

Author: Susurrus

src/sys/ioctl/mod.rs

@@ -85,9 +85,7 @@
 //! `_IOC`, _IOR`, `_IOW`, and `_IORW` map to "none", "read", "write", and "readwrite"
 //! respectively.
 //!
-//! Some `ioctl`s can operate on arrays of objects, so there are `read buf`, `write buf`, and
-//! `readwrite buf` forms as well. These generate functions that include a `len` argument to
-//! specify the length of the array:
+//! More examples on using `ioctl!` can be found in the [rust-spidev crate](https://github.com/rust-embedded/rust-spidev).
 //!
 //! ```text
 //! pub unsafe fn $NAME(fd: c_int, val: *mut u8, len: usize) -> Result<c_int>;
@@ -128,13 +126,13 @@
 //!
 //! More examples on using `ioctl!` can be found in the [rust-spidev crate](https://github.com/rust-embedded/rust-spidev).
 //!
-//! How do I get the magic numbers?
-//! ===============================
+//! Finding ioctl documentation
+//! ---------------------------
 //!
 //! For Linux, look at your system's headers. For example, `/usr/include/linux/input.h` has a lot
-//! of lines defining macros which use `_IOR`, `_IOW`, `_IOC`, and `_IORW`. Finding documentation
-//! on some of those `ioctl`s can be trickier, however, though some are documented in the manpages
-//! and others are documented directly in the source.
+//! of lines defining macros which use `_IOR`, `_IOW`, `_IOC`, and `_IORW`. Some `ioctl`s are
+//! documented directly in the headers defining their constants, but others have more extensive
+//! documentation in man pages (like termios' `ioctl`s which are in `tty_ioctl(4)`).
 #[cfg(any(target_os = "linux", target_os = "android"))]
 #[path = "platform/linux.rs"]
 #[macro_use]