All this can be integrated into an environment command:
=> setenv upd_fdt 'tftp 1800000 a3m071/a3m071.dtb;run mtdargs addip2 addtty; \
- fdt addr 1800000;fdt boardsetup;erase fc060000 fc07ffff; \
+ fdt addr 1800000;fdt boardsetup;fdt chosen;erase fc060000 fc07ffff; \
cp.b 1800000 fc060000 10000'
=> saveenv