guide: Describe how extended platform compatibility check

Change-Id: I100359f746c6d4eb7ebbf909e23d375727b17b96

diff --git a/doc/GUIDE.md b/doc/GUIDE.md
index 891d69b..a33e861 100644 (file)
--- a/doc/GUIDE.md
+++ b/doc/GUIDE.md
@@ -239,10 +239,15 @@ image, then this `ISU package` is **removed** (`/opt/isu/<pkg_name>` is removed
 `ISU package` (`/opt/isu/<pkg_name>`) is **restored** by the standard `OS upgrade` read-write
 check-pointing mechanism.
 
-Lastly, if the `OS upgrade` changes the platform version (e.g. from `Tizen 6.5` to `Tizen 7.0`),
-then all ISU packages are removed unconditionally. For this comparison, the `TZ_BUILD_RELEASE_NAME`
-constant from the `/etc/tizen-build.conf` file is used.
-
+Lastly, if the `OS upgrade` changes the platform in incompatible manner then all ISU packages
+are removed unconditionally. `platform_major_version_fields` in `/etc/isu/upgrade.cfg` is used
+to define which variables from isu.cfg must match between platform and isu package for platform
+to be assumed compatible. Following fields may be set and are checked by default (all must match):
+* `tz_build_release_name` (eg. `Tizen8.0/Unified`)
+* `tz_build_arch` (eg. `aarch64`)
+* `model_name` (eg. `TizenIOT`)
+* `manufacturer` (eg. `Tizen`)
+* `device_type` (eg. `IoT_Headless`)
 
 ## Preparing new `ISU packages`