documented how to create hybrid ROM

Makefile

@@ -201,6 +201,20 @@ updatebin:
 	@$(TOOL_RELEASE) -i ./build -o ./bin $(patsubst build/%,%,$(REL_TARGET_LIST))
 	@cp build/chargen_openroms.rom bin/chargen_openroms.rom
 
+# Rules - external blobs
+
+kernal:
+	@echo
+	@echo Please copy \'kernal\' file from the original ROM set to the \'open-roms\' directory
+	@echo
+	@exit 1
+
+basic:
+	@echo
+	@echo Please copy \'basic\' file from the original ROM set to the \'open-roms\' directory
+	@echo
+	@exit 1
+
 # Rules - tools
 
 $(DIR_ACME) $(SRC_ACME):

bin/README.md

@@ -2,12 +2,12 @@
 Follow these rules, or bad things will happen!
 
 
-- Don't mix ROMs for different platforms - use generic BASIC with generic KERNAL, Ultimate64 BASIC with Ultimate64 KERNAL, etc.
+* Don't mix ROMs for different platforms - use generic BASIC with generic KERNAL, Ultimate64 BASIC with Ultimate64 KERNAL, etc.
 
-- Don't mix these ROMs with any other ROMs; exceptions:
+* Don't mix these ROMs with any other ROMs; exceptions:
 
    - kernal_hybrid.rom, which is meant to be used (and has to be used) with the original BASIC ROM;
-     however, this hybrid ROM cannot be distributed due to legal/copyright reasons
+     however, this hybrid ROM cannot be distributed due to legal/copyright reasons; see [here](./../doc/Hybrid-build.md) for instruction how to create it
 
    - chargen_*.rom - these ones are fully interchangeable
 
@@ -22,6 +22,4 @@ Have fun!
 ------
 
 
-PXL font was created by Retrofan, we got a permission to include it with Open ROMs under GNU Lesser General Public License 3.0, see:
-
-- https://www.forum64.de/index.php?thread/84000-neuer-c64-systemfont-auch-plus4-c128-atari/&postID=1493383#post1493383
+PXL font was created by Retrofan, we got a permission to include it with Open ROMs under GNU Lesser General Public License 3.0, see [here](https://www.forum64.de/index.php?thread/84000-neuer-c64-systemfont-auch-plus4-c128-atari/&postID=1493383#post1493383).

doc/Hybrid-build.md

@@ -0,0 +1,13 @@
+
+The C64 ROM is typically distributed in 2 files 8 KB each, one called *kernal*, one *basic*. This might be misleading, as the C64 Kernal takes about 6.5 KB, and the BASIC about 9.5 KB - some parts of BASIC is therefore placed in the *kernal* file. This is the main reason you can't easily use the Open ROMs Kernal file with original C64 BASIC.
+
+But it is still possible to combine them:
+* copy the *kernal* file to the *open-roms* main directory
+* from the Linux command line type `make test_hybrid` - this will crate the hybrid Kernal file, *open-roms/bin/kernal_hybrid.rom*, and launch VICE emulator with it
+
+Sorry, no Windows support (but it should work under *Windows Subsystem for Linux* if GCC and libpng devel packages are installed), and no macOS support (I don't have a machine to test).
+
+Please note, that it is illegal to distribute such a hybrid ROM:
+
+* it contains proprietary Commodore/Microsoft code
+* it contains LGPL 3 licensed Open ROMs code combined with code not available under compatible license