Documentation: Add ISA bus driver documentation

This is a verbatim copy of the original commit message of the initial
commit of the ISA bus driver authored by Rene Herman. Descriptions of
the module_isa_driver macro and max_num_isa_dev macro are provided at
the end.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index 1d5b4be..92a1906 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5995,6 +5995,13 @@
 F:	kernel/irq/irqdomain.c
 F:	kernel/irq/msi.c
 
+ISA
+M:	William Breathitt Gray <vilhelm.gray@gmail.com>
+S:	Maintained
+F:	Documentation/isa.txt
+F:	drivers/base/isa.c
+F:	include/linux/isa.h
+
 ISAPNP
 M:	Jaroslav Kysela <perex@perex.cz>
 S:	Maintained