docs: split into multiple files

The overview.txt file has evolved into more than just an overview.
Split it into chapters, and include the misc tutorials.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

1 files changed, 64 insertions, 0 deletions

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+File.........: 6 - Toolchain types.txt
+Copyrigth....: (C) 2010 Yann E. MORIN <yann.morin.1998@anciens.enib.fr>
+License......: Creative Commons Attribution Share Alike (CC-by-sa), v2.5
+
+
+Toolchain types  /
+________________/
+
+
+There are four kinds of toolchains you could encounter.
+
+First off, you must understand the following: when it comes to compilers there
+are up to four machines involved:
+  1) the machine configuring the toolchain components: the config machine
+  2) the machine building the toolchain components:    the build machine
+  3) the machine running the toolchain:                the host machine
+  4) the machine the toolchain is generating code for: the target machine
+
+We can most of the time assume that the config machine and the build machine
+are the same. Most of the time, this will be true. The only time it isn't
+is if you're using distributed compilation (such as distcc). Let's forget
+this for the sake of simplicity.
+
+So we're left with three machines:
+ - build
+ - host
+ - target
+
+Any toolchain will involve those three machines. You can be as pretty sure of
+this as "2 and 2 are 4". Here is how they come into play:
+
+1) build == host == target
+    This is a plain native toolchain, targetting the exact same machine as the
+    one it is built on, and running again on this exact same machine. You have
+    to build such a toolchain when you want to use an updated component, such
+    as a newer gcc for example.
+    crosstool-NG calls it "native".
+
+2) build == host != target
+    This is a classic cross-toolchain, which is expected to be run on the same
+    machine it is compiled on, and generate code to run on a second machine,
+    the target.
+    crosstool-NG calls it "cross".
+
+3) build != host == target
+    Such a toolchain is also a native toolchain, as it targets the same machine
+    as it runs on. But it is build on another machine. You want such a
+    toolchain when porting to a new architecture, or if the build machine is
+    much faster than the host machine.
+    crosstool-NG calls it "cross-native".
+
+4) build != host != target
+    This one is called a canadian-toolchain (*), and is tricky. The three
+    machines in play are different. You might want such a toolchain if you
+    have a fast build machine, but the users will use it on another machine,
+    and will produce code to run on a third machine.
+    crosstool-NG calls it "canadian".
+
+crosstool-NG can build all these kinds of toolchains (or is aiming at it,
+anyway!)
+
+(*) The term Canadian Cross came about because at the time that these issues
+    were all being hashed out, Canada had three national political parties.
+    http://en.wikipedia.org/wiki/Cross_compiler