README: Add note about vendor file names

README.md

@@ -77,7 +77,7 @@ cargo +nightly doc --features <chip> --open
 *avr-device* is generated using [`atdf2svd`](https://github.com/Rahix/atdf2svd) and [`svd2rust`](https://github.com/rust-embedded/svd2rust).  The vendor-provided *atdf* files can be found in `vendor/`.  The intermediate svd files are patched by `svdpatch.py` (Adapted from [`svdpatch.py`](https://github.com/stm32-rs/stm32-rs/blob/master/scripts/svdpatch.py) in [stm32-rs](https://github.com/stm32-rs/stm32-rs)) with device-dependent patches in `patch/`, mainly to improve undescriptive names and missing descriptions.
 
 ### Adding a new Chip
-To add a new chip, download the *atdf* from <http://packs.download.atmel.com/> (or [avr-mcu/packs/](https://github.com/avr-rust/avr-mcu/tree/master/packs)) and place it in `vendor/`.  Be sure to name it like the Rust module that should be generated.  Next, you need to integrate it into the base crate and build system.  Follow what was done in commit [290613454fbd ("Add basic support for ATmega64")](https://github.com/Rahix/avr-device/commit/290613454fbdc5e4ac98e53deccaf74dafc88963).  Please adhere to the alphabetical sorting that is present so far.
+To add a new chip, download the *atdf* from <http://packs.download.atmel.com/> (or [avr-mcu/packs/](https://github.com/avr-rust/avr-mcu/tree/master/packs)) and place it in `vendor/` ***note: file name may need to be modified***.  Be sure to name it like the Rust module that should be generated.  Next, you need to integrate it into the base crate and build system.  Follow what was done in commit [290613454fbd ("Add basic support for ATmega64")](https://github.com/Rahix/avr-device/commit/290613454fbdc5e4ac98e53deccaf74dafc88963).  Please adhere to the alphabetical sorting that is present so far.
 
 Next, you **must** create a `<chipname>.yaml` in `patch/` which has at least the following content:
 ```yaml