Dear community, dear Sascha,

an accident happened on my side. I totally overlooked that after my initial mail with the 
initial quoted error message the message changed.

Probably either the change of compiling the dtb file (make dtbs DTC_FLAGS=-@) got
me a __symbols__ node or another thing was sorted out by me on accident meanwhile
since still I am trying to get used to device tree handling.

In detail, this messages are not valid any more:

>>>> Loading ARM Linux zImage '/boot/uImage'
>>>> Loading devicetree from '/boot/am335x-boneblack.dtb'
>>>> ERROR: of_resolver: __symbols__ missing from base devicetree
>>>> WARNING: Failed to fixup node in of_overlay_fixup+0x1/0x4: Invalid argument
>>>> ERROR: of_resolver: __symbols__ missing from base devicetree
>>>> WARNING: Failed to fixup node in of_overlay_fixup+0x1/0x4: Invalid argument

but I get a different set of errors. Probably since including Friday and I overlooked this.
How embarassing, sorry!

Now I get:

ERROR: of_resolver: cannot find node ocp in base devicetree
WARNING: Failed to fixup node in of_overlay_fixup+0x1/0x4: Invalid argument
ERROR: of_resolver: cannot find node ocp in base devicetree
WARNING: Failed to fixup node in of_overlay_fixup+0x1/0x4: Invalid argument

which is very reasonable: 

> Have a look at the generated dtb file with 'dtc -I dtb -O dts <file>'.
> It should contain a __symbols__ node.

The decompiled result of “my” dtb has a __symbols__ note at the bottom of the file, yes!
I suppose each “fragment@n {target = XYZ …”) in a overlay has to have a matching 
counterpart XYZ in the __symbols__ node in the base file, right? Because in my overlay
there is an "target = <&ocp>!" without a matching counterpart in the base dtb.
Two other entries (uart1, am33xx_pinmux) have a matching entry. 

> BTW do you have a good reason to use overlays? Overlays only have a

No indeed I don’t necessarily - I realized meanwhile by myself.

Additionally I relaized the overlays I have here in question only do some GPIO
multiplexing I can do by hand/script in the /sys gpio section anyway. Only interesting
for serial line availability at boot. May be later it’s interesting for us for different
variante, I hope I am used to this stuff then. 

> value when you have different hardware variants in which different
> overlays are loaded. If that's not the case I'd just go with a static
> devicetree and be done with it.

For now I agree and I try to understand how to enable the UART1 and UART4
in a static dtb way and I currently search the vanille device tree on how to do 
this and how this currently this is done at least with the working UART0 :-)

Sadly not barebox related :-)

Kind Regards
Konsti