Hi Wolfgang,
sorry to answer that late.
Sorry to disagree. Of course U-Boot at whole will not fit into a NAND block. But you can place all the assembler initialization stuff including NAND relocation into the first block. The relocation code then reads the remaining NAND sectors and appends it to the one already read by the CPU. For the S3C2410 I did post a patch half a year ago.
What you describe is exactly such a different bootstap loader.
Not exactly It is part of U-Boot as just the relocation code of U-Boot is modified as it now needs to copy from NAND but not from NOR. And care must be taken that this code is in a specific memory range (first NAND block) while normally there are no limits on its position. Technically it is same to some other boot loaders like (lilo, grub) that have different steps when booting of hard disk.
Best regards,