{
       . = 0x10000;
       .text : { *(.text) }
       . = 0x8000000;
       .data : { *(.data) }
       .bss : { *(.bss) }
     }

   You write the 'SECTIONS' command as the keyword 'SECTIONS', followed
by a series of symbol assignments and output section descriptions
enclosed in curly braces.

   The first line inside the 'SECTIONS' command of the above example
sets the value of the special symbol '.', which is the location counter.
If you do not specify the address of an output section in some other way
(other ways are described later), the address is set from the current
value of the location counter.  The location counter is then incremented
by the size of the output section.  At the start of the 'SECTIONS'
command, the location counter has the value '0'.

   The second line defines an output section, '.text'.  The colon is
required syntax which may be ignored for now.  Within the curly braces
after the output section name, you list the names of the input sections
which should be placed into this output section.  The '*' is a wildcard
which matches any file name.  The expression '*(.text)' means all
'.text' input sections in all input files.

   Since the location counter is '0x10000' when the output section
'.text' is defined, the linker will set the address of the '.text'
section in the output file to be '0x10000'.

   The remaining lines define the '.data' and '.bss' sections in the
output file.  The linker will place the '.data' output section at
address '0x8000000'.  After the linker places the '.data' output
section, the value of the location counter will be '0x8000000' plus the
size of the '.data' output section.  The effect is that the linker will
place the '.bss' output section immediately after the '.data' output
section in memory.

   The linker will ensure that each output section has the required
alignment, by increasing the location counter if necessary.  In this
example, the specified addresses for the '.text' and '.data' sections
will probably satisfy any alignment constraints, but the linker may have
to create a small gap between the '.data' and '.bss' sections.

   That's it!  That's a simple and complete linker script.