Is there difference between embedded linux kernel and desktop linux kernel?
I think there is a one linux kernel support all devices(arm,arm64,x86/x64 etc.), and developers make distribute like debian(for desktop)/raspian(for embedded), arch/archarm. Is that true?
yes, there is one official kernel for different architectures at kernel.org
There may be forks with special hardware handling, additional drivers, etc. for specific customers (hardware suppliers like Samsung)
But your assumption is 90% true ;)