ld: Extend documentation for EXCLUDE_FILE

There was a gap in the documentation of EXCLUDE_FILE that could cause
confusion to a user.  When writing an input section specifier like this:

    *(EXCLUDE_FILE (somefile.o) .text .text.*)

this could mean one of the following:

   1. All '.text' and '.text.*' from all files except for 'somefile.o',
   or
   2. All '.text' from all files except 'somefile.o', and all '.text.*'
   sections from all files.

It turns out that the second interpretation is correct, but the manual
does not make this clear (to me at least).  Hopefully this patch makes
things clearer.

ld/ChangeLog:

	* ld/ld.texinfo (Input Section Basics): Expand the description of
	EXCLUDE_FILE.

ld/ChangeLog

@@ -1,3 +1,8 @@
+2016-09-20  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* ld/ld.texinfo (Input Section Basics): Expand the description of
+	EXCLUDE_FILE.
+
 2016-09-14  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	* testsuite/ld-arm/cmse-veneers.s: Add a test for ARMv8-M Security

ld/ld.texinfo

@@ -4214,6 +4214,21 @@ they are found in the linker input.  In the second example, all
 @samp{.text} input sections will appear first, followed by all
 @samp{.rdata} input sections.
 
+When using EXCLUDE_FILE with more than one section, the exclusion only
+applies to the section immediately following, for example:
+@smallexample
+*(EXCLUDE_FILE (*somefile.o) .text .rdata)
+@end smallexample
+@noindent
+will cause all @samp{.text} sections from all files except
+@file{somefile.o} to be included, while all @samp{.rdata} sections
+from all files, including @file{somefile.o}, will be included.  To
+exclude the @samp{.rdata} sections from @file{somefile.o} the example
+should be modified to:
+@smallexample
+*(EXCLUDE_FILE (*somefile.o) .text EXCLUDE_FILE (*somefile.o) .rdata)
+@end smallexample
+
 You can specify a file name to include sections from a particular file.
 You would do this if one or more of your files contain special data that
 needs to be at a particular location in memory.  For example: