doc: update README

README.md

@@ -2,70 +2,98 @@
 
 [![Crates.io](https://img.shields.io/crates/v/uefi)](https://crates.io/crates/uefi)
 [![Docs.rs](https://docs.rs/uefi/badge.svg)](https://docs.rs/uefi)
-![Stars](https://img.shields.io/github/stars/rust-osdev/uefi-rs)
 ![License](https://img.shields.io/github/license/rust-osdev/uefi-rs)
 ![Build status](https://github.com/rust-osdev/uefi-rs/workflows/Rust/badge.svg)
+![Stars](https://img.shields.io/github/stars/rust-osdev/uefi-rs)
 
 ## Description
 
-[UEFI] is the successor to the BIOS. It provides an early boot environment for
-OS loaders, hypervisors and other low-level applications. While it started out
-as x86-specific, it has been adopted on other platforms, such as ARM.
+[UEFI] started as the successor firmware to the BIOS in x86 space and developed
+to a universal firmware specification for various platforms, such as ARM. It
+provides an early boot environment with a variety of [specified][spec]
+ready-to-use "high-level" functionality, such as accessing disks or the network.
+EFI images, the files that can be loaded by an UEFI environment, can leverage
+these abstractions to extend the functionality in form of additional drivers,
+OS-specific bootloaders, or different kind of low-level applications.
+
+Our mission is to provide **safe** and **performant** wrappers for UEFI
+interfaces, and allow developers to write idiomatic Rust code.
+
+This repository provides various crates:
+
+- `uefi-raw`: Raw Rust UEFI bindings for basic structures and functions.
+- `uefi`: High-level wrapper around various low-level UEFI APIs. \
+  Most probably, you want to use this crate.
+- `uefi-services`: Optional Rust convenience with a global allocator and a
+  `log`-based logger implementation.
 
-This crate makes it easy to both:
-  - Write UEFI applications in Rust (for `i686`, `x86_64`, or `aarch64`)
-  - Call UEFI functions from an OS (usually built with a [custom target][rustc-custom])
+You can use the abstractions for example to:
 
-The objective is to provide **safe** and **performant** wrappers for UEFI interfaces,
-and allow developers to write idiomatic Rust code.
+- create OS-specific loaders and leverage UEFI boot service
+- access UEFI runtime services from an OS
 
-Check out [the UEFI application template](template) for a quick start.
+All crates are compatible with all platforms that both the Rust compiler and
+UEFI support, such as `i686`, `x86_64`, and `aarch64`). Please note that we
+can't test all possible hardware/firmware/platform combinations.
 
 [UEFI]: https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface
-[rustc-custom]: https://doc.rust-lang.org/rustc/targets/custom.html
 
-![uefi-rs running in QEMU](https://imgur.com/SFPSVuO.png)
+![UEFI App running in QEMU](https://imgur.com/SFPSVuO.png)
+Screenshot of an application running in QEMU on an UEFI firmware that leverages
+our Rust library.
+
+## User Documentation
+
+For a quick start, please check out [the UEFI application template](template).
+
+The [uefi-rs book] contains a tutorial, how-tos, and overviews of some important
+UEFI concepts. Reference documentation for the various crates can be found on
+[docs.rs]:
+
+- [docs.rs/uefi](https://docs.rs/uefi)
+- [docs.rs/uefi-macros](https://docs.rs/uefi-macros)
+- [docs.rs/uefi-raw](https://docs.rs/uefi-raw)
+- [docs.rs/uefi-services](https://docs.rs/uefi-services)
+
+For additional information, refer to the [UEFI specification][spec].
+
+[spec]: https://uefi.org/specs/UEFI/2.10
+[uefi-rs book]: https://rust-osdev.github.io/uefi-rs/HEAD
+[docs.rs]: https://docs.rs
+
+### MSRV
 
-## Project structure
+See the [uefi package's README](uefi/README.md#MSRV).
+
+## Developer Guide
+
+### Project structure
 
 This project contains multiple sub-crates:
 
 - `uefi`: defines the standard UEFI tables / interfaces.
   The objective is to stay unopinionated and safely wrap most interfaces.
 
-- `uefi-macros`: procedural macros that are used to derive some traits in `uefi`.
+- `uefi-macros`: procedural macros that are used to derive some traits
+  in `uefi`.
 
 - `uefi-raw`: raw types that closely match the definitions in the UEFI
   Specification. Safe wrappers for these types are provided by the `uefi`
   crate. The raw types are suitable for implementing UEFI firmware.
 
-- `uefi-services`: provides a panic handler, and initializes the `alloc` / `logger` features.
+- `uefi-services`: provides a panic handler, and initializes
+  the `alloc` / `logger` features.
 
 - `uefi-test-runner`: a UEFI application that runs unit / integration tests.
 
 [log]: https://github.com/rust-lang-nursery/log
 
-## Documentation
-
-The [uefi-rs book] contains a tutorial, how-tos, and overviews of some
-important UEFI concepts.
-
-Reference documentation can be found on docs.rs:
-- [docs.rs/uefi](https://docs.rs/uefi)
-- [docs.rs/uefi-macros](https://docs.rs/uefi-macros)
-- [docs.rs/uefi-raw](https://docs.rs/uefi-raw)
-- [docs.rs/uefi-services](https://docs.rs/uefi-services)
-
-For additional information, refer to the [UEFI specification][spec].
-
-[spec]: http://www.uefi.org/specifications
-[uefi-rs book]: https://rust-osdev.github.io/uefi-rs/HEAD
-
-## Building and testing uefi-rs
+### Building and testing uefi-rs
 
 Use the `cargo xtask` command to build and test the crate.
 
 Available commands:
+
 - `build`: build all the UEFI packages
   - `--release`: build in release mode
   - `--target {x86_64,ia32,aarch64}`: choose target UEFI arch
@@ -77,9 +105,10 @@ Available commands:
   - `--warnings-as-errors`: treat warnings as errors
 - `run`: build `uefi-test-runner` and run it in QEMU
   - `--ci`: disable some tests that don't work in the CI
-  - `--disable-kvm`: disable hardware accelerated virtualization support in QEMU.
-                     Especially useful if you want to run the tests under
-                     [WSL](https://docs.microsoft.com/en-us/windows/wsl) on Windows.
+  - `--disable-kvm`: disable hardware accelerated virtualization support in
+    QEMU.
+    Especially useful if you want to run the tests under
+    [WSL](https://docs.microsoft.com/en-us/windows/wsl) on Windows.
   - `--example <NAME>`: run an example instead of the main binary.
   - `--headless`: run QEMU without a GUI
   - `--ovmf-code <PATH>`: path of an OVMF code file
@@ -94,18 +123,16 @@ most of the library's functionality.
 Check out the testing project's [`README.md`](uefi-test-runner/README.md) for
 prerequisites for running the tests.
 
-## MSRV
-
-See the [uefi package's README](uefi/README.md#MSRV).
-
 ## Contributing
 
-We welcome issues and pull requests! For instructions on how to set up a development
-environment and how to add new protocols, check out [CONTRIBUTING.md](CONTRIBUTING.md).
+We welcome issues and pull requests! For instructions on how to set up a
+development environment and how to add new protocols, check out
+[CONTRIBUTING.md](CONTRIBUTING.md).
 
 ## License
 
 The code in this repository is licensed under the Mozilla Public License 2.
-This license allows you to use the crate in proprietary programs, but any modifications to the files must be open-sourced.
+This license allows you to use the crate in proprietary programs, but any
+modifications to the files must be open-sourced.
 
 The full text of the license is available in the [license file](LICENSE).